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Infectious Disease and Microbiology – Pleural Effusion and Fever Basics and Definitions A pleural effusion is the accumulation of fluid in the pleural space due to increased production or decreased absorption. Light’s criteria distinguish transudates from exudates with high sensitivity and specificity. An exudative effusion meets at least one of the following: pleural fluid protein/serum protein >0.5, pleural fluid LDH/serum LDH >0.6, or pleural fluid LDH greater than two-thirds the upper limit of normal serum LDH. Parapneumonic effusions occur secondary to bacterial pneumonia and are classified as uncomplicated (free-flowing, sterile, resolve with antibiotics), complicated (low pH, low glucose, loculated), or empyema (gross pus in the pleural space). Empyema may be simple (single locule) or complex (multiloculated), most commonly caused by Streptococcus pneumoniae. Clinical Approach Symptoms depend on etiology and include dyspnea, pleuritic chest pain, fever, weight loss, edema, and hemoptysis. Evaluation requires careful history, physical examination, and diagnostic thoracentesis. Initial pleural fluid analysis includes protein, LDH, glucose, amylase, cytology, and cell count. In febrile patients or when fluid is turbid or malodorous, Gram stain, aerobic and anaerobic cultures are essential, with consideration of pH, acid-fast bacilli smear and culture, and fungal studies. Pleural biopsy and bronchoscopy are indicated when tuberculosis or malignancy is suspected. Thoracoscopy or open pleural biopsy is reserved for unresolved diagnostic cases. Epidemiology Pleural effusions account for approximately 1.5 million cases annually in the United States. Tuberculosis is the leading cause of exudative effusions worldwide but is less common in the US. In intensive care units, about 10% of pleural effusions are parapneumonic. Etiology Transudative effusions result from systemic factors and are rarely associated with fever; causes include heart failure, nephrotic syndrome, cirrhosis, constrictive pericarditis, pulmonary embolism, and myxedema. Exudative effusions arise from local pleural disease and commonly present with fever; causes include infections (bacterial, mycobacterial, fungal, viral, parasitic), malignancy, pulmonary embolism, and connective tissue diseases. Other causes include pancreatitis, esophageal rupture, chylothorax, hemothorax, drug reactions, asbestos-related disease, post-cardiac injury syndromes, radiation, sarcoidosis, uremia, and yellow nail syndrome. In patients with AIDS, noninfectious causes predominate, though bacterial pneumonia, Pneumocystis jirovecii, tuberculosis, and disseminated fungal infections remain important. Tuberculous pleurisy is typically an exudate with low pH, normal-to-low glucose, and lymphocytic predominance. Vertebral osteomyelitis, hantavirus pulmonary syndrome, parasitic infections, and Chagas disease should also be considered in appropriate settings. Diagnosis Acute febrile illness with chest pain and leukocytosis suggests aerobic bacterial pneumonia with parapneumonic effusion. Subacute presentations with weight loss and aspiration risk suggest anaerobic infection. Tuberculous pleuritis presents with fever, dyspnea, pleuritic pain, and weight loss, though pleural pain may be absent. Diagnostic Tests and Interpretation Neutrophil-predominant effusions suggest parapneumonic effusion, pulmonary embolism, or pancreatitis, while lymphocyte predominance favors tuberculosis, malignancy, or rheumatologic disease. Eosinophilic effusions occur in hemothorax, parasitic disease, asbestos exposure, pulmonary embolism, and Churg–Strauss syndrome. Low pleural glucose (<60 mg/dL) and low pH (<7.3) indicate complicated infection, malignancy, or rheumatoid pleuritis. Acid-fast stains and cultures have low sensitivity in tuberculous pleurisy; pleural biopsy significantly improves diagnostic yield. ADA levels >70 U/L and elevated interferon-γ support tuberculosis, with reduced utility in low-prevalence regions. Elevated pleural amylase suggests pancreatic disease, lung adenocarcinoma, or esophageal rupture. Imaging includes chest radiography, ultrasound for septations, CT for parenchymal disease or embolism, and PET scanning for suspected malignancy. Management Uncomplicated parapneumonic effusions require antibiotics alone. Complicated effusions require tube thoracostomy, often with intrapleural fibrinolytics. Persistent loculated effusions or empyema require thoracoscopy or decortication. Simple empyema is managed with large-bore chest tubes; complex empyema often necessitates surgical intervention. Follow-Up and Prognosis Persistently unexplained effusions require reevaluation for tuberculosis and pulmonary embolism. Untreated tuberculous pleurisy frequently progresses to active tuberculosis within several years, mandating full antituberculous therapy. Tuberculous empyema may lead to severe pleural fibrosis and restrictive lung disease. 
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Infectious Disease and Microbiology – Neurological Symptoms and Signs with Fever Overview and Definitions Clouding of consciousness refers to mild inattentiveness and slightly reduced wakefulness. Obtundation describes slowed responses to external stimuli with decreased alertness and increased sleepiness. Coma is a state of unarousable unconsciousness with no purposeful response to pain. Encephalitis is inflammation of the brain associated with neurologic or mental status changes. Meningitis is inflammation of the meninges surrounding the central nervous system and may be acute, presenting over hours, or chronic, lasting longer than four weeks. Clinical Approach Fever with neurologic symptoms requires urgent evaluation for central nervous system infection, systemic infection, or noninfectious neurologic pathology. History should include onset and progression of neurologic symptoms, medication and substance use, trauma, travel, animal exposures, immunocompromised states, and past medical history, with collateral history when available. A complete physical examination should be performed with emphasis on dermatologic, head and neck, cardiopulmonary, and a comprehensive neurologic assessment including mental status, cranial nerves, funduscopy, gait, tone, power, reflexes, sensation, and cerebellar function. Level of consciousness should be documented using the Glasgow Coma Scale. Examination for meningitis includes assessment of neck stiffness, Kernig and Brudzinski signs, and jolt accentuation of headache. Funduscopic examination is important to detect papilledema, subarachnoid hemorrhage, or hypertensive encephalopathy. Epidemiology Herpes simplex virus type 1 accounts for approximately 10% of encephalitis cases. In regions where tuberculosis is endemic, tuberculomas are a frequent cause of intracranial mass lesions. The annual incidence of bacterial meningitis in the United States is approximately 1.5 per 100,000 population. In adults, the most common pathogens are Streptococcus pneumoniae, Neisseria meningitidis, and Listeria monocytogenes, with Staphylococcus aureus, including methicillin-resistant strains, increasingly recognized. Etiology Acute fever with neurologic signs suggests bacterial meningitis, encephalitis, or infectious intracranial lesions, all of which are medical emergencies. CNS granulomas may be caused by syphilis, cysticercosis, tuberculoma, fungal infections, or sarcoidosis. Enteroviruses are the most common cause of aseptic meningitis. Opportunistic infections are common in advanced HIV infection. Listeria rhombencephalitis presents with brainstem and cranial nerve involvement and is best identified on MRI. Parasitic causes include Echinococcus granulosus, schistosomiasis, amebiasis, and paragonimiasis. Fungal causes include Cryptococcus neoformans, Histoplasma, Coccidioides, Blastomyces, Aspergillus, mucormycosis, and Pseudallescheria. Viral cerebellar encephalitis may follow measles, varicella, Lyme disease, rabies, or legionellosis. Free-living amoebae such as Naegleria fowleri cause acute fulminant meningitis, while Acanthamoeba and Balamuthia cause chronic meningoencephalitis. Noninfectious causes include drug intoxication or withdrawal, malignancy, and subarachnoid hemorrhage. Clinical Features Bacterial meningitis typically presents with acute onset of fever, headache, neck stiffness, photophobia, nausea, and vomiting. Absence of headache and jolt accentuation makes bacterial meningitis unlikely, although individual clinical features lack sensitivity. Central nervous system tuberculosis is commonly associated with fever. Brucellosis may cause chronic granulomatous meningitis with constitutional symptoms and relevant animal exposure. Diagnostic Evaluation Initial investigations include complete blood count, electrolytes, renal and liver function tests, and blood cultures. Lumbar puncture is essential unless contraindicated by raised intracranial pressure or coagulopathy and should include opening pressure, cell count with differential, protein, glucose, Gram stain, culture, mycobacterial and fungal studies, cryptococcal antigen, syphilis testing, and PCR for herpes simplex or varicella zoster virus. Neuroimaging with CT or MRI is required to exclude space-occupying lesions, with MRI offering superior sensitivity for encephalitis and brainstem disease. In bacterial meningitis, cerebrospinal fluid typically shows elevated opening pressure, neutrophilic pleocytosis, high protein, and low or normal glucose. Viral meningitis usually demonstrates lower white cell counts with lymphocytic predominance and moderately elevated protein. Management Empiric treatment for suspected bacterial meningitis includes a third- or fourth-generation cephalosporin combined with vancomycin, with ampicillin added in patients over 50 years of age or immunocompromised to cover Listeria. Dexamethasone should be administered early when pneumococcal meningitis is suspected. Acyclovir should be initiated if herpes simplex encephalitis is a consideration. Antimicrobial therapy must not be delayed for imaging or lumbar puncture when meningitis is suspected. Additional Care Management often requires a multidisciplinary approach, with involvement of physiotherapy, occupational therapy, and speech and language pathology during recovery. Follow-Up and Prognosis Early recognition and prompt treatment are critical to reducing morbidity and mortality associated with infectious neurologic syndromes. Complications Complications include death, deafness, visual impairment, seizures, stroke, cognitive impairment, and increased intracranial pressure.  Emergency and Acute Medicine – Lymphocytosis Overview and Definition Lymphocytosis is defined as an absolute lymphocyte count greater than 4,000 cells/mm³ in peripheral blood. It may be reactive or neoplastic in origin. Reactive lymphocytosis is caused by infectious or noninfectious conditions, whereas neoplastic lymphocytosis reflects underlying hematologic malignancy. Infectious causes include viral, bacterial, protozoal, and parasitic diseases, while noninfectious causes include drugs, autoimmune disorders, and certain endocrinopathies. Atypical lymphocytes are non-neoplastic, activated lymphocytes that appear in response to immunologic stimulation; they are typically large, with nucleoli, irregular cytoplasm, and may appear to “indent” surrounding red blood cells on smear. Clinical Approach History and physical examination are essential to distinguish reactive from neoplastic lymphocytosis. Age is an important clue: acute EBV infection is common in children and young adults, while chronic lymphocytic leukemia is more common after the fifth decade. Assess symptom duration, vaccination history, prior illnesses, and medication use. Evaluate risk factors for HIV and tuberculosis, including sexual exposure, intravenous drug use, close contacts, travel, homelessness, and institutionalization. A detailed travel history should assess risk for food-, water-, and arthropod-borne infections. Physical examination should focus on lymphadenopathy and organ involvement such as hepatomegaly or splenomegaly. Many clinically stable patients without systemic toxicity can be evaluated as outpatients. Peripheral blood smears should be reviewed by experienced personnel, as atypical lymphocytes may be subtle. Epidemiology Lymphocytosis is common across many clinical conditions. Evidence of prior EBV infection is present in over 90% of adults. Primary EBV infection is frequent and often asymptomatic in children. CMV seroprevalence increases with age, exceeding 90% in adults over 80 years. Acute HIV infection may present with atypical lymphocytosis and a mononucleosis-like illness. Tuberculosis remains highly prevalent worldwide, with a large reservoir of latent infection. Etiology Common infectious causes include EBV, CMV, HIV, adenovirus, influenza, hepatitis A and B, measles, mumps, rubella, dengue, rickettsial infections, pertussis, tuberculosis, Bartonella, Brucella, syphilis, Q fever, Mycoplasma pneumoniae, toxoplasmosis, malaria, and babesiosis. Noninfectious causes include drug and toxic reactions, post-perfusion syndrome, immunizations, radiation exposure, endocrine disorders such as thyrotoxicosis or adrenal insufficiency, autoimmune diseases, smoking, and stress-related catecholamine release. Malignant causes include acute and chronic lymphocytic leukemia, lymphomas, hairy cell leukemia, and paraneoplastic syndromes. Other causes include sarcoidosis, thymoma, myasthenia gravis, Guillain–Barré syndrome, serum sickness, graft rejection, and inherited immune disorders. Clinical Features Acute EBV, CMV, or HIV infection may present with fever, lymphadenopathy, pharyngitis, fatigue, and anorexia. EBV typically causes exudative pharyngitis and hepatosplenomegaly, while CMV more often presents with prolonged fever and less prominent organomegaly. Cat-scratch disease presents with localized lymphadenopathy near the inoculation site. Cycling (Pel–Ebstein) fevers raise concern for Hodgkin lymphoma. Generalized lymphadenopathy is seen in many infections, leukemias, lymphomas, and sarcoidosis. Massive splenomegaly suggests myeloproliferative disorders, lymphomas, malaria, visceral leishmaniasis, or storage diseases. Viral hepatitis may present with jaundice and right upper quadrant tenderness. Diagnostic Evaluation Peripheral blood smear review is essential, and prior blood counts should be reviewed to assess chronicity. EBV infection is characterized by atypical lymphocytosis, positive heterophile antibody testing, and mild transaminitis. The Monospot test is highly specific and moderately sensitive. EBV serology distinguishes acute from past infection. CMV diagnosis relies on IgM and IgG serology, with PCR reserved for immunocompromised patients. HIV testing includes antigen–antibody screening with confirmatory testing; PCR is required in suspected acute infection. Toxoplasmosis is diagnosed by serology. Respiratory viruses such as influenza are detected by nasopharyngeal swab, with PCR offering the highest sensitivity. If malignancy is suspected, further evaluation may include flow cytometry, bone marrow biopsy, and cytogenetic studies. Imaging is reserved for clinical indications such as suspected pneumonia, organomegaly, or focal neurologic findings. Management Treatment is directed at the underlying cause. Uncomplicated EBV infection requires supportive care only. Patients with hepatosplenomegaly should avoid contact sports for up to two months due to risk of splenic rupture. Antibiotics such as ampicillin may cause rash in EBV infection and should be avoided. CMV treatment is generally reserved for immunocompromised patients. HIV infection requires antiretroviral therapy under specialist care. Medications Supportive therapy with acetaminophen or NSAIDs is appropriate for uncomplicated viral infections. Corticosteroids may be used for airway compromise in EBV. Antiviral therapy for CMV includes ganciclovir or valganciclovir in selected patients. Herpesvirus infections may be treated with acyclovir or valacyclovir. Influenza is treated with neuraminidase inhibitors when indicated. Follow-Up and Prognosis Patients should be counseled regarding warning signs and complications, particularly in EBV infection. Liver enzymes should be monitored until normalization. Persistent or unexplained lymphocytosis warrants hematology consultation to exclude malignancy.  Emergency and Acute Medicine – Lymphadenopathy and Fever Overview and Definitions Lymphadenitis refers to inflammation of one or more lymph nodes, while lymphangitis involves inflammation of lymphatic channels; both may occur in acute or chronic disease. Mesenteric lymphadenitis results from inflammation of mesenteric nodes and may clinically mimic acute appendicitis. In most regions, lymph nodes larger than 1 cm are abnormal; epitrochlear nodes greater than 0.5 cm and inguinal nodes greater than 1.5–2 cm are considered enlarged, although palpable inguinal nodes are common in healthy adults. Generalized lymphadenopathy is defined as involvement of two or more noncontiguous nodal regions. Clinical Approach Fever commonly accompanies lymphadenopathy, with infection being the leading cause. Lymph node enlargement may be incidental or the primary presenting feature, and clinicians must determine whether observation or further investigation is required. A detailed history and comprehensive physical examination are essential. Duration is informative, as suppurative infections usually present within one week, whereas chronic lymphadenopathy suggests infections such as HIV or tuberculosis, malignancy, inflammatory, or autoimmune disease. Epidemiologic factors including travel, sick contacts, and animal exposure should be assessed. Associated symptoms include weight loss, fever, night sweats, sore throat, cough, pruritus, fatigue, lymph node pain, and myalgia or arthralgia. Examination should include all nodal regions to determine whether disease is localized or generalized, along with abdominal assessment for hepatosplenomegaly. Findings such as anemia, petechiae, or bleeding suggest bone marrow infiltration. While many infections cause fever with lymphadenopathy, pathogens such as Francisella tularensis, Bartonella henselae, and mycobacteria often present with a single prominent lymph node and fever. Epidemiology More than two-thirds of patients presenting to primary care with lymphadenopathy have nonspecific or upper respiratory causes. The likelihood of malignancy increases with age, particularly over 50 years. In primary care, approximately 1% of patients with lymphadenopathy have an underlying malignancy. Acute mesenteric lymphadenitis is more common in children. In developed countries, mycobacterial lymphadenopathy is more often due to nontuberculous species. Etiology Infectious causes include viral infections such as Epstein–Barr virus, cytomegalovirus, herpes simplex virus, dengue, rubella, measles, HIV, and West Nile virus; bacterial infections including streptococci, Staphylococcus aureus, Bartonella henselae, brucellosis, tularemia, plague, melioidosis, tuberculosis, nontuberculous mycobacteria, listeriosis, leptospirosis, secondary syphilis, diphtheria, typhoid fever, and lymphogranuloma venereum; fungal infections such as histoplasmosis, coccidioidomycosis, paracoccidioidomycosis, and cryptococcosis; parasitic infections including toxoplasmosis, leishmaniasis, trypanosomiasis, and filariasis; and rickettsial diseases. Immunologic causes include systemic lupus erythematosus, rheumatoid arthritis, vasculitides, Still’s disease, dermatomyositis, graft-versus-host disease, juvenile idiopathic arthritis, mixed connective tissue disease, serum sickness, and Sjögren’s syndrome. Malignant causes include Hodgkin and non-Hodgkin lymphomas, acute and chronic leukemias, hairy cell leukemia, amyloidosis, sarcomas, and metastatic disease. Other causes include lipid storage disorders, endocrine diseases such as hyperthyroidism and Addison disease, Castleman disease, Kikuchi disease, drug reactions, familial Mediterranean fever, and Kawasaki disease. In HIV infection, lymphadenopathy ranges from early follicular hyperplasia to opportunistic infections and malignancies, with common causes including lymphoma, mycobacterial infection, toxoplasmosis, systemic fungal infection, and bacillary angiomatosis. Diagnostic Evaluation Assessment of lymph nodes should document size, shape, consistency, mobility, and tenderness. Hard nodes suggest carcinoma, rubbery firm non-tender nodes are typical of lymphoma, and tender mobile nodes usually indicate reactive infection. Some malignancies, such as acute leukemia, may cause rapid enlargement with pain. Initial laboratory evaluation should be guided by risk factors and may include blood cultures, HIV testing, syphilis serology, heterophile antibody testing, toxoplasma, CMV, EBV serologies, Bartonella serology, urine histoplasma antigen, autoimmune markers, and other targeted tests. Fine-needle aspiration can be useful, but excisional biopsy provides superior diagnostic yield, particularly for lymphoma. Lymph node specimens should be evaluated with cultures, mycobacterial and fungal stains, cytology, and molecular diagnostics. Chest radiography may reveal pulmonary or mediastinal involvement. Ultrasonography is useful for superficial nodes, while CT or MRI better evaluate deep nodal disease and guide biopsy. PET imaging identifies metabolically active nodes. In the absence of high-risk features, observation for 2–4 weeks is appropriate, with biopsy indicated if lymphadenopathy persists. Management Treatment depends on the underlying etiology and should be directed at the identified cause. Empiric therapy may be required in severe infection, while malignancy or autoimmune disease requires disease-specific management. Follow-Up and Prognosis In patients without features concerning for malignancy or severe infection, clinical observation for 2–4 weeks after initial evaluation is appropriate before proceeding to biopsy. Complications Delayed diagnosis or treatment of infectious lymphadenopathy may lead to disseminated or severe infection.  Emergency and Acute Medicine – Lung Nodules Overview and Definitions Pulmonary nodules are rounded opacities surrounded by lung parenchyma and are typically less than 3–4 cm in diameter; larger lesions are classified as lung masses. Pathologically, a pulmonary nodule is a small, approximately spherical, circumscribed focus of abnormal tissue, while radiologically it is defined as a round opacity, at least moderately well marginated, and no more than 3 cm in maximum diameter. Linear or planar opacities are not considered nodules. Chest imaging may reveal a solitary pulmonary nodule, often referred to as a coin lesion, or multiple pulmonary nodules. Clinical Approach The primary objective is to distinguish benign from malignant nodules. Evaluation begins with a thorough history, as the probability of malignancy increases with age and is rare in patients younger than 35 years. Important malignancy risk factors include prior lung cancer, family history of lung cancer, cigarette smoking, second-hand smoke exposure, occupational carcinogen exposure such as asbestos or radon, pulmonary fibrosis, chronic obstructive pulmonary disease, and alpha-1 antitrypsin deficiency. A higher cumulative smoking burden is associated with increased cancer risk. If malignancy is suspected, it is essential to determine whether the lesion represents a primary lung cancer or metastatic disease. Fever suggests an infectious etiology, and immunocompromised patients are at risk for opportunistic infections presenting as solitary or multiple nodules. Physical examination may reveal signs of malignancy including cachexia, anemia, jaundice, clubbing, bone pain, abdominal masses, or superior vena cava syndrome. Radiologic features such as size, distribution, shape, calcification pattern, cavitation, lymphadenopathy, pleural effusion, and clustering provide diagnostic clues. Low-risk nodules may be followed with serial CT imaging, whereas larger or suspicious nodules warrant biopsy, PET imaging, or video-assisted thoracoscopic surgery. Empiric antimicrobial therapy should be initiated in immunocompromised patients or those at risk for rapid deterioration. Epidemiology Pulmonary nodules are common, with up to 51% of smokers aged 50 years or older having nodules detected on CT. Fewer than 1% of nodules smaller than 5 mm are malignant in patients without a history of cancer. The likelihood of malignancy increases with size: approximately 0.2% for nodules under 3 mm, 0.9% for 4–7 mm, 18% for 8–20 mm, and greater than 50% for nodules larger than 20 mm. Male smokers have a tenfold increased risk of lung cancer compared with nonsmokers, rising to 15–35 times higher in heavy smokers. Paragonimus westermani infection can present as a lung nodule in endemic regions of East and Southeast Asia. Tuberculosis commonly presents with hilar lymphadenopathy, and histoplasmosis is the most frequent cause of hospitalization from endemic mycoses in the United States. Etiology and Pathophysiology Solitary pulmonary nodules may be caused by primary lung malignancies including adenocarcinoma, squamous cell carcinoma, large cell carcinoma, and small cell carcinoma, as well as metastatic disease from breast, head and neck, thyroid, melanoma, colon, kidney, sarcoma, and germ cell tumors. Other causes include carcinoid tumors, infections such as bacterial abscesses, tuberculosis, atypical mycobacteria, histoplasmosis, blastomycosis, coccidioidomycosis, cryptococcosis, aspergilloma, nocardiosis, Pneumocystis infection, and parasitic infections including echinococcosis, dirofilariasis, ascariasis, and paragonimiasis. Benign neoplasms include hamartoma, lipoma, and fibroma. Non-neoplastic causes include arteriovenous malformations, bronchogenic cysts, granulomatosis with polyangiitis, sarcoidosis, rheumatoid nodules, amyloidoma, rounded atelectasis, intrapulmonary lymph nodes, hematoma, pulmonary infarction, and mucoid impaction. Multiple pulmonary nodules are more often benign when less than 1 cm, but in patients with known malignancy, nodules larger than 0.5 cm are more likely metastatic. Infectious causes of multiple nodules include septic emboli, fungal infections, tuberculosis, atypical mycobacteria, and paragonimiasis, while inflammatory conditions such as sarcoidosis, rheumatoid arthritis, and vasculitis are also common causes. Diagnostic Evaluation History should assess for tuberculosis risk factors, immunosuppression, aspiration risk, and exposure to endemic fungi. Lung abscesses may arise from aspiration, tricuspid valve endocarditis, or septic thrombophlebitis such as Lemierre syndrome, often in patients with poor dentition or prolonged recumbency. Symptoms include cough, sputum production, dyspnea, fever, night sweats, weight loss, and anorexia. Laboratory evaluation may include blood cultures, sputum Gram stain and culture, fungal cultures, acid-fast bacilli staining and mycobacterial cultures, cryptococcal antigen testing, galactomannan and beta-D-glucan assays, and serologic testing for endemic fungi. Imaging with high-resolution CT can detect nodules as small as 1–2 mm. Benign calcification patterns include homogeneous, central, concentric, and popcorn calcifications, while malignant features include eccentric or amorphous calcification and spiculated borders. Ground-glass halos suggest invasive fungal infection, particularly aspergillosis. PET imaging identifies metabolically active lesions. Transthoracic echocardiography is indicated when septic emboli are suspected, and CT of the neck should be performed if Lemierre syndrome is considered. Percutaneous biopsy or VATS is indicated when malignancy risk is high. Management Empiric antibiotics should be initiated in patients with fever or systemic toxicity after obtaining blood cultures. Suspected tuberculosis requires differentiation between latent and active disease using clinical assessment, imaging, and sputum studies. Mild pulmonary histoplasmosis may not require treatment, but persistent or moderate-to-severe disease is treated with itraconazole or amphotericin B followed by itraconazole. Lung abscesses are typically polymicrobial and treated with beta-lactam/beta-lactamase inhibitors or clindamycin. Voriconazole is first-line therapy for invasive aspergillosis, with surgical debridement considered when feasible. Paragonimiasis is treated with praziquantel or triclabendazole. Follow-Up and Prognosis Malignant solitary pulmonary nodules typically double in volume over 20–400 days. Low-risk nodules smaller than 1 cm may be monitored with serial CT imaging, while high-risk nodules should be surgically excised. PET scanning is most useful for nodules larger than 1 cm with intermediate malignancy risk to guide management decisions. Complications Untreated lung abscesses may progress to respiratory failure requiring mechanical ventilation. Cavitation may occur in infectious, malignant, and inflammatory nodules, and cavitary lesions are frequently complicated by secondary Aspergillus infection.  Emergency and Acute Medicine – Joint Pain and Fever Overview and Definitions Joint pain accompanied by fever suggests an inflammatory or infectious process and requires prompt evaluation. Joint involvement may be monoarticular, oligoarticular, or polyarticular and may be symmetric or asymmetric. Arthritis refers to inflammation of a joint and is a clinical finding rather than a diagnosis, whereas arthralgia denotes joint pain without objective inflammation. Acute joint disorders last less than six weeks, while chronic disorders persist beyond this duration. Clinical Approach The presence of fever narrows the differential diagnosis toward infectious, crystal-induced, immune-mediated, or reactive etiologies. Noninflammatory disorders such as osteoarthritis or fibromyalgia are rarely associated with fever. History should focus on onset and tempo of symptoms, recent infections, travel, trauma, sexual exposure, immunosuppression, and prior joint disease. Physical examination should assess for warmth, erythema, swelling, effusion, and limitation of motion, as well as extra-articular features such as rash, cardiac murmurs, or enthesitis. Synovial fluid aspiration and analysis are mandatory in acute monoarthritis or when infection or crystal disease is suspected. Epidemiology Septic arthritis is usually monoarticular, with polyarticular involvement occurring in 10–20% of adults. Risk factors include diabetes mellitus, chronic kidney disease, malignancy, immunosuppression, intravenous drug use, trauma, prosthetic joints, and underlying joint disease. Musculoskeletal manifestations occur in up to 45% of patients with infective endocarditis. Viral outbreaks, particularly chikungunya, have caused large numbers of cases of acute febrile polyarthritis, especially among travelers. Etiology and Pathophysiology Septic arthritis is the most important diagnosis to exclude and is most commonly caused by Staphylococcus aureus. Other infectious causes include disseminated gonococcal infection, endocarditis, Lyme disease, Whipple’s disease, secondary syphilis, and mycobacterial or fungal infections. Viral etiologies include parvovirus B19, acute HIV infection, hepatitis B, dengue virus, and chikungunya. Noninfectious causes include gout, pseudogout, acute rheumatic fever, adult-onset Still’s disease, systemic lupus erythematosus, vasculitis, and rarely malignancy. Diagnostic Evaluation Synovial fluid analysis is central to diagnosis. Bacterial arthritis is suggested by leukocyte counts greater than 50,000 cells/µL with polymorphonuclear predominance, turbid appearance, and low viscosity. Gram stain and culture should always be performed, and blood cultures obtained in acute presentations. Gonococcal arthritis frequently yields negative synovial cultures, requiring sampling of mucosal sites. Elevated ESR and CRP favor bacterial infection, while markedly elevated ferritin levels suggest adult-onset Still’s disease. Management Suspected septic arthritis requires immediate empiric antimicrobial therapy after appropriate cultures are obtained. Most cases of nongonococcal septic arthritis require surgical drainage or joint washout. Gonococcal arthritis is usually managed medically with ceftriaxone. NSAIDs provide symptomatic relief in viral and reactive arthritis. Early joint immobilization followed by gradual mobilization is recommended once infection is controlled. Complications Delayed or inadequate treatment of septic arthritis may result in irreversible joint destruction, osteomyelitis, bacteremia, and systemic sepsis.  Infectious Diseases and Microbiology: Insect Bites and Stings Basics Description Zoonoses are infections transmitted from nonhuman animals to humans, and vectors are the animals responsible for transmission. Insect bites and stings can lead to a wide spectrum of infectious diseases with acute, subacute, or highly variable presentations. Noninfectious reactions such as anaphylaxis and inflammatory responses are also common. Approach to the Patient Clinical evaluation requires awareness of geographic distribution, vector life cycles, and characteristic clinical syndromes. A detailed history of mosquito or tick exposure and the timing of bites can help narrow the differential diagnosis. Travel history is critical and should include dates, destinations, stopovers, pretravel medical advice, vaccinations, malaria prophylaxis, and preventive measures such as bed nets or repellents. Laboratory confirmation may support the diagnosis but is often unavailable early in illness. Multiple infections can follow a single exposure, as some vectors transmit more than one pathogen simultaneously. Malaria must always be considered in febrile travelers returning from endemic regions and treated as a medical emergency; given the risk of severe outcomes, empiric antimicrobial therapy is often appropriate when suspicion is high. Epidemiology Hundreds of thousands of Lyme disease cases have been reported in the United States, with most occurring in the Northeast, Minnesota, and Wisconsin. Rocky Mountain spotted fever occurs throughout the Americas, predominantly in the southern and southeastern United States, with higher incidence in warmer months. West Nile virus has been present in the US since 1999, with tens of thousands of reported cases; most infections are asymptomatic, and true exposure rates are likely much higher. Eastern equine encephalitis is a rare but severe mosquito-borne viral infection found mainly along the East and Gulf coasts, reported sporadically over decades. Malaria remains an important imported infection, with over a thousand cases reported annually in the US. General Prevention In areas with tick exposure, preventive strategies include wearing protective clothing and using proper tick-removal techniques with fine tweezers, avoiding crushing or abrupt removal. Insect repellents containing DEET remain the most effective option, particularly when combined with permethrin-treated clothing. Concentrations of 10–30% DEET provide strong protection; higher concentrations do not significantly increase efficacy. Plant-based repellents such as picaridin, PMD, or citronella have some benefit but are less effective than DEET. Etiology In the United States, clinicians may encounter both local and imported vector-borne diseases. Mosquitoes transmit malaria, dengue, West Nile virus, yellow fever, chikungunya, and viral encephalitides including eastern equine encephalitis. Ticks transmit Lyme disease, babesiosis, ehrlichiosis, anaplasmosis, Rocky Mountain spotted fever, tularemia, southern tick–associated rash illness, Bartonella infection, tick paralysis, and other rickettsioses. Flies may transmit bartonellosis, African trypanosomiasis, filariasis, onchocerciasis, leishmaniasis, or cause myiasis. Fleas transmit plague, murine typhus, and tungiasis. Diagnosis Incubation periods and symptom patterns vary by pathogen. Falciparum malaria typically incubates for about two weeks and presents with fever, chills, headache, abdominal or neck pain, nausea, vomiting, and sometimes jaundice. West Nile virus incubates for up to two weeks; most cases are asymptomatic, while symptomatic illness usually causes short-lived fever, myalgias, headache, and sometimes rash, with possible neurologic involvement. Colorado tick fever presents after several days with biphasic fever, severe headache, photophobia, and myalgias, occasionally with a transient rash. Dengue usually incubates for several days to two weeks and classically causes fever, retro-orbital headache, rash, and marked muscle and joint pain. bisnes Nenek dia Diagnostic Tests and Interpretation Laboratory evaluation depends on the suspected condition. Blood smears are mandatory in febrile patients returning from malaria-endemic regions. Lyme disease is diagnosed by serology with enzyme immunoassay confirmed by Western blot in compatible cases. Babesiosis is identified on blood smear by intraerythrocytic parasites, with PCR and serology as adjuncts. West Nile virus infection is diagnosed by IgM detection in serum or cerebrospinal fluid. Neuroimaging in eastern equine encephalitis often reveals characteristic thalamic and basal ganglia abnormalities. Treatment Management depends on the specific infection and is detailed in disease-specific references. Given the severity of some vector-borne illnesses, prompt empiric therapy is often warranted when clinical suspicion is high. Ongoing Care and Complications Eastern equine encephalitis carries a high mortality rate, and many survivors have permanent neurologic disability. Delayed diagnosis and treatment of falciparum malaria significantly increase mortality and the risk of permanent neurologic damage. Lyme disease may involve the nervous system or cardiac conduction pathways, leading to neurologic deficits or arrhythmias. Dengue may cause mucosal bleeding and exacerbate preexisting gastrointestinal lesions. Colorado tick fever has been associated with rare but serious complications including encephalitis, meningitis, hemorrhage, myocarditis, orchitis, atypical pneumonia, and hepatitis.  Infectious Diseases and Microbiology: Insect Bites and Stings Basics Description Zoonoses are infections transmitted from nonhuman animals to humans, and vectors are the animals responsible for transmission. Insect bites and stings can lead to a wide spectrum of infectious diseases with acute, subacute, or highly variable presentations. Noninfectious reactions such as anaphylaxis and inflammatory responses are also common. Approach to the Patient Clinical evaluation requires awareness of geographic distribution, vector life cycles, and characteristic clinical syndromes. A detailed history of mosquito or tick exposure and the timing of bites can help narrow the differential diagnosis. Travel history is critical and should include dates, destinations, stopovers, pretravel medical advice, vaccinations, malaria prophylaxis, and preventive measures such as bed nets or repellents. Laboratory confirmation may support the diagnosis but is often unavailable early in illness. Multiple infections can follow a single exposure, as some vectors transmit more than one pathogen simultaneously. Malaria must always be considered in febrile travelers returning from endemic regions and treated as a medical emergency; given the risk of severe outcomes, empiric antimicrobial therapy is often appropriate when suspicion is high. Epidemiology Hundreds of thousands of Lyme disease cases have been reported in the United States, with most occurring in the Northeast, Minnesota, and Wisconsin. Rocky Mountain spotted fever occurs throughout the Americas, predominantly in the southern and southeastern United States, with higher incidence in warmer months. West Nile virus has been present in the US since 1999, with tens of thousands of reported cases; most infections are asymptomatic, and true exposure rates are likely much higher. Eastern equine encephalitis is a rare but severe mosquito-borne viral infection found mainly along the East and Gulf coasts, reported sporadically over decades. Malaria remains an important imported infection, with over a thousand cases reported annually in the US. General Prevention In areas with tick exposure, preventive strategies include wearing protective clothing and using proper tick-removal techniques with fine tweezers, avoiding crushing or abrupt removal. Insect repellents containing DEET remain the most effective option, particularly when combined with permethrin-treated clothing. Concentrations of 10–30% DEET provide strong protection; higher concentrations do not significantly increase efficacy. Plant-based repellents such as picaridin, PMD, or citronella have some benefit but are less effective than DEET. Etiology In the United States, clinicians may encounter both local and imported vector-borne diseases. Mosquitoes transmit malaria, dengue, West Nile virus, yellow fever, chikungunya, and viral encephalitides including eastern equine encephalitis. Ticks transmit Lyme disease, babesiosis, ehrlichiosis, anaplasmosis, Rocky Mountain spotted fever, tularemia, southern tick–associated rash illness, Bartonella infection, tick paralysis, and other rickettsioses. Flies may transmit bartonellosis, African trypanosomiasis, filariasis, onchocerciasis, leishmaniasis, or cause myiasis. Fleas transmit plague, murine typhus, and tungiasis. Diagnosis Incubation periods and symptom patterns vary by pathogen. Falciparum malaria typically incubates for about two weeks and presents with fever, chills, headache, abdominal or neck pain, nausea, vomiting, and sometimes jaundice. West Nile virus incubates for up to two weeks; most cases are asymptomatic, while symptomatic illness usually causes short-lived fever, myalgias, headache, and sometimes rash, with possible neurologic involvement. Colorado tick fever presents after several days with biphasic fever, severe headache, photophobia, and myalgias, occasionally with a transient rash. Dengue usually incubates for several days to two weeks and classically causes fever, retro-orbital headache, rash, and marked muscle and joint pain. Diagnostic Tests and Interpretation Laboratory evaluation depends on the suspected condition. Blood smears are mandatory in febrile patients returning from malaria-endemic regions. Lyme disease is diagnosed by serology with enzyme immunoassay confirmed by Western blot in compatible cases. Babesiosis is identified on blood smear by intraerythrocytic parasites, with PCR and serology as adjuncts. West Nile virus infection is diagnosed by IgM detection in serum or cerebrospinal fluid. Neuroimaging in eastern equine encephalitis often reveals characteristic thalamic and basal ganglia abnormalities. Treatment Management depends on the specific infection and is detailed in disease-specific references. Given the severity of some vector-borne illnesses, prompt empiric therapy is often warranted when clinical suspicion is high. Ongoing Care and Complications Eastern equine encephalitis carries a high mortality rate, and many survivors have permanent neurologic disability. Delayed diagnosis and treatment of falciparum malaria significantly increase mortality and the risk of permanent neurologic damage. Lyme disease may involve the nervous system or cardiac conduction pathways, leading to neurologic deficits or arrhythmias. Dengue may cause mucosal bleeding and exacerbate preexisting gastrointestinal lesions. Colorado tick fever has been associated with rare but serious complications including encephalitis, meningitis, hemorrhage, myocarditis, orchitis, atypical pneumonia, and hepatitis.  Infectious Diseases and Microbiology: Hepatosplenomegaly and Fever Basics Description A midclavicular liver span of at least 12.5 cm supports hepatomegaly. Splenomegaly is defined as a spleen exceeding 250 g or one that is palpable, and on ultrasound is suggested by a cephalocaudal length of 13 cm or more . Approach to the Patient Evaluating Hepatomegaly Palpate to identify the lower liver edge at the right midclavicular line, then use gentle percussion to define the upper border so liver span can be measured; a span ≥12.5 cm supports hepatomegaly. Because hyperinflated lungs can push the liver downward, the upper border must be assessed to avoid overcalling enlargement. Evaluating Splenomegaly Bedside assessment should include both palpation and percussion. Palpation is best done bimanually with the patient supine and in the right lateral position. Percussion methods by Nixon and Castell provide the best diagnostic performance. In Nixon’s method, the patient lies on the right side and percussion begins in the posterior axillary line at the level where lung resonance ends, moving obliquely toward the left anterior costal margin; a dullness span over 8 cm suggests splenomegaly and has moderate sensitivity with high specificity. In Castell’s method, the patient is supine and percussion in the lowest intercostal space at the left anterior axillary line should remain resonant during inspiration if the spleen is normal; this approach has moderate sensitivity and specificity. If missing splenomegaly would change management, confirm with ultrasound or scintigraphy. Evaluating Fever with Liver and/or Spleen Enlargement Obtain a comprehensive history emphasizing travel and immigration, occupation, sexual history, intravenous drug use, animal exposure, and family history of malignancy, connective tissue disease, or inherited conditions. Look for associated findings including jaundice, fever duration and pattern, lymphadenopathy, rashes or bite exposures, liver edge texture and tenderness, an enlarged gallbladder or other abdominal mass, and spleen size and consistency. Initial testing commonly includes broad laboratory evaluation, heterophile antibody testing, hepatitis studies, imaging, and in selected cases bone marrow evaluation, endoscopy, and/or liver biopsy. Epidemiology In young adults, palpability of the liver and spleen can occur even without disease. In a large sample of healthy military personnel, the liver was not palpable or only at the costal margin in over half, and descended only 1–2 cm below the margin in many others. Studies of healthy college entrants have found a small proportion with unexplained palpable spleens, and palpable spleens have been reported in a notable minority of otherwise normal postpartum women. Etiology Hepatomegaly with Fever Infectious causes include pyogenic or amoebic abscess, ascending cholangitis, chronic granulomatous disease, chronic Q fever, ehrlichiosis, histoplasmosis, HIV, infectious hepatitis, infectious mononucleosis, leptospirosis, syphilis, tuberculosis, and parasitic infections. Malignant causes include diffuse primary hepatic cancer, diffuse metastases, myeloproliferative disorders, lymphoma, and angiosarcoma. Inflammatory causes include sarcoidosis, autoimmune hepatitis, familial Mediterranean fever, and Still’s disease. Splenomegaly with Fever Infectious causes include viral infections such as hepatitis, infectious mononucleosis, and HIV; bacterial infections such as endocarditis, pyogenic abscess, salmonellosis, leptospirosis, brucellosis, Bartonella; fungal infections such as histoplasmosis; mycobacterial infections including miliary tuberculosis and nontuberculous mycobacteria; and parasitic infections including malaria, toxoplasmosis, amoebic liver abscess, schistosomiasis with Katayama fever, visceral leishmaniasis, babesiosis, and ehrlichiosis. Inflammatory causes include rheumatoid arthritis, sarcoidosis, systemic lupus erythematosus, and hemophagocytic lymphohistiocytosis. Malignant causes include lymphoma, acute and chronic leukemias, and myelodysplastic or myeloproliferative syndromes. Numerous parasites can enlarge liver and spleen depending on exposure context, including malaria, schistosomiasis, hydatid disease, leishmaniasis, toxocariasis, toxoplasmosis, liver flukes such as Fasciola hepatica, and echinococcal cysts, which can enlarge organs but are rarely febrile. Fever occurs in roughly half of toxoplasmosis and toxocariasis cases. Diagnosis History and Clinical Manifestations In young adults, the combination of fatigue, sore throat, fever, lymphadenopathy, and hepatosplenomegaly is most often infectious mononucleosis. Fever with abdominal pain that may localize to the right upper quadrant, vomiting or anorexia, hepatomegaly, leukocytosis with elevated sedimentation rate, and otherwise unexplained anemia should raise concern for liver abscess. Pyogenic liver abscess most often arises from biliary disease and is commonly due to enteric organisms including Escherichia coli, Klebsiella, enterococci, anginosus group streptococci, and anaerobes, and is most often seen in adults in their fifth and sixth decades. Pyogenic liver abscess with metastatic infection such as endophthalmitis, meningitis, or other focal abscesses suggests Klebsiella pneumoniae, particularly in patients with diabetes and those from East Asia. Amoebic liver abscess is now most often seen in travelers and migrants; men have markedly higher risk of invasive Entamoeba histolytica disease including liver abscess, gastrointestinal symptoms such as nausea, vomiting, or diarrhea occur in a minority, and presentation may occur years after exposure. In HIV with advanced immunosuppression, fever with lymphadenopathy and splenomegaly is often mycobacterial, but lymphoma must be ruled out. Leptospirosis should be considered with compatible exposures and fever with rigors, headache, and myalgias, with severe disease involving pulmonary, hepatic, and renal dysfunction, aseptic meningitis, and bleeding tendencies. In tropical settings, splenomegaly may reflect hyper-reactive malarial splenomegaly, characterized by fever, anemia, weight loss, abdominal discomfort, lassitude, abnormal liver tests, elevated IgM, and hepatic sinusoidal lymphocytosis. Physical Examination Beyond confirming fever and organ enlargement, search for diagnostic clues such as lymphadenopathy suggesting lymphoma, infectious mononucleosis, brucellosis, schistosomiasis, HIV, or mycobacterial infection; rashes suggesting schistosomiasis, rickettsial disease, leishmaniasis, mononucleosis, Still’s disease, or syphilis; pharyngeal findings supporting mononucleosis; murmurs or embolic phenomena supporting endocarditis, Bartonella, or brucellosis; jaundice supporting viral hepatitis, cholangitis, or leptospirosis; conjunctival suffusion supporting leptospirosis; and joint findings supporting rheumatoid arthritis, lupus, or Still’s disease. Diagnostic Tests and Interpretation Laboratory Studies Leukocytosis with a left shift supports bacterial infection. Marked lymphocytosis with atypical lymphocytes on smear supports infectious mononucleosis and can be confirmed early with heterophile antibody testing or with EBV viral capsid antigen IgM. Eosinophilia can accompany certain parasitic causes of hepatosplenomegaly but is not typical of amoebic infection. Three sets of blood cultures off antibiotics help exclude most endocarditis, while Bartonella, Brucella, and Q fever are better assessed by serology. Based on exposure history, obtain HIV, syphilis, and viral hepatitis testing, and consider serologies for rickettsial disease, Entamoeba, toxoplasma, schistosomiasis, Q fever, Fasciola, leptospirosis, and ehrlichiosis, along with blood films for malaria and babesiosis. Include biochemistry, autoimmune markers, and ferritin when inflammatory disease is considered. If imaging identifies an abscess, image-guided aspiration can establish diagnosis. Excisional lymph node biopsy or liver biopsy offers the highest yield for lymphoma. Bone marrow biopsy or splenic aspirate can diagnose leishmaniasis, with PCR or serology as alternatives. Imaging Ultrasound can confirm enlargement and identify causes such as abscess, hepatocellular carcinoma, or biliary pathology. Contrast-enhanced CT is helpful when ultrasound is nondiagnostic and suspicion remains for focal lesions or lymphoma. MRI is rarely needed but may help distinguish abscess from malignancy. Treatment Medications Therapy is directed by the underlying diagnosis. Confirmed liver abscess requires antibiotics targeting likely organisms; pyogenic abscess is generally managed with percutaneous drainage plus antibiotics, with surgery reserved for failed drainage or complex multiloculated disease. Praziquantel is effective for Schistosoma mansoni in advanced hepatosplenic disease and is preferred when Schistosoma haematobium coinfection is present. Fascioliasis is typically treated with triclabendazole 10 mg/kg for one to two days; bithionol is an alternative, and the role of praziquantel is uncertain. Ongoing Care and Follow-Up Advise patients with splenomegaly to avoid contact sports and monitor for spontaneous rupture, which almost always presents with severe upper abdominal pain that often starts in the left upper quadrant, spreads more diffusely, and can radiate to the left shoulder. Complications In the United States, spontaneous splenic rupture is most commonly associated with infectious mononucleosis. Although rare, occurring in a small fraction of mononucleosis cases, it is the leading cause of death related to infectious mononucleosis.  Infectious Diseases and Microbiology: Gonorrhea Basics Description Gonorrhea is caused by Neisseria gonorrhoeae, a gram-negative intracellular diplococcus that infects humans only. Spread occurs through direct mucosal inoculation during sexual contact or childbirth. Transmission is more efficient from men to women, and a single sexual exposure can infect up to half of female partners. Epidemiology Gonorrhea remains a major global public health issue and contributes substantially to morbidity, especially in developing regions. Worldwide incidence has been estimated at roughly 62 million new infections annually, with highest rates in sub-Saharan Africa, South and Southeast Asia, the Caribbean, and Latin America. In the United States, hundreds of thousands of cases were reported in 2008 with the highest rates in females aged 15–19 and males aged 20–24; reported rates were higher in African American and Hispanic populations than in White populations. Risk Factors Risk is increased by female sex, age under 25, prior gonorrhea or other STIs, new or multiple partners, inconsistent condom use, commercial sex work, drug use, and travel to high-prevalence countries. General Prevention Control relies on early detection, immediate treatment at diagnosis, and treatment of sexual partners. Partners within 60 days before symptom onset should be evaluated and treated. Delaying sexual debut, reducing partner number, and consistent condom use decrease transmission. Etiology Disease is due to N. gonorrhoeae, a nonmotile, non–spore-forming gram-negative diplococcus. Commonly Associated Conditions Coinfection with other STIs is common; Chlamydia coinfection occurs in about one-third of cases. Gonorrhea also increases susceptibility to acquiring HIV. Diagnosis Clinical manifestations depend on infection site, bacterial strain, host factors, sex, and coinfections. Many infections are asymptomatic in both sexes. Incubation is typically 2–7 days. In men, urethritis usually begins with dysuria followed by purulent discharge, and acute epididymitis is the most frequent complication. In women, urethritis can cause dysuria, frequency, and urgency, and cervicitis may develop with purulent discharge, cramping, dyspareunia, and postcoital or intermenstrual bleeding; symptoms often intensify around menstruation. Untreated infection can ascend, causing pelvic inflammatory disease with infertility and chronic pelvic pain. Conjunctivitis usually results from autoinoculation and can rapidly threaten vision. In neonates, infection is commonly ophthalmia neonatorum acquired during delivery; ocular prophylaxis with agents such as silver nitrate drops or tetracycline ointment is used for prevention. Disseminated gonococcal infection may present with fever, rash, tenosynovitis, and septic arthritis and can resemble an influenza-like illness without obvious mucosal symptoms, so urethral/cervical, rectal, and pharyngeal sites should be sampled. Diagnostic Tests and Interpretation Laboratory Studies In symptomatic men, Gram stain of urethral discharge can show polymorphonuclear cells and gram-negative intracellular diplococci, but Gram stain performs poorly with endocervical, rectal, and pharyngeal specimens. Culture allows antimicrobial susceptibility testing and should be performed on selective media such as modified Thayer–Martin (or equivalent) with aerobic conditions and increased CO₂; rapid processing is essential because gonococci do not tolerate drying. Strains linked to dissemination may be more fastidious and harder to grow. Nucleic acid–based tests can detect N. gonorrhoeae from swabs or urine with sensitivity and specificity comparable or better than culture, but cost is higher and cross-reactivity with nonpathogenic Neisseria species can occur. Differential Diagnosis Urethritis can be nongonococcal due to Chlamydia, Ureaplasma, Mycoplasma genitalium, Haemophilus vaginalis, HSV, adenovirus, and others. Vaginal symptoms may reflect candidiasis, bacterial vaginosis, trichomoniasis, or noninfectious etiologies such as chemical irritation, allergy, fistula, or pregnancy-related leukorrhea. Disseminated gonococcal infection must be distinguished from meningococcemia, ecthyma gangrenosum, other bacteremias, septic arthritis from other bacteria, and reactive arthritis. Treatment Medications CDC-recommended therapy has centered on cephalosporins. For uncomplicated urethral, cervical, or rectal infection, recommended single-dose options include ceftriaxone 125 mg IM, cefixime 400 mg PO, or spectinomycin 2 g IM. Pharyngeal infection is harder to eradicate and is treated with ceftriaxone 125 mg IM as the preferred regimen. Gonococcal conjunctivitis is treated with ceftriaxone 125 mg IM once, with saline eye irrigation as an optional adjunct. Disseminated infection is treated with parenteral cephalosporin-based regimens such as ceftriaxone 1 g IM/IV daily or cefotaxime/ceftizoxime 1 g IV three times daily, or spectinomycin 2 g IM twice daily; continue parenteral therapy for 24–48 hours after clinical improvement, then transition to an oral agent such as cefixime 400 mg PO twice daily to complete a total of one week. If chlamydial infection has not been excluded, provide concurrent chlamydia therapy. Fluoroquinolones are not recommended as first-line therapy in the United States because of widespread resistance. Additional Treatment Because Chlamydia coinfection is common, initial management should cover chlamydia (e.g., azithromycin or doxycycline) unless it has been ruled out. Ongoing Care and Follow-Up Patient Monitoring A routine test-of-cure is not required after treating uncomplicated infection. If symptoms persist, obtain culture with susceptibility testing; the most common reason for apparent treatment failure is reinfection from an untreated partner. Patient Education Advise consistent condom use and provide instruction on correct condom use. Complications The most important complication is pelvic inflammatory disease from ascending infection, which can lead to tubo-ovarian abscess, pelvic peritonitis, and Fitz-Hugh–Curtis syndrome, with long-term infertility and chronic pelvic pain. In men, complications include epididymitis, periurethritis, balanitis, acute or chronic prostatitis, orchitis, seminal vasculitis, and infection of Tyson and Cowper glands. Disseminated gonococcemia is more common in women, with menstruation increasing risk, and typically causes tenosynovitis, migratory arthritis, and peripheral skin lesions that may be maculopapular or pustular; blood cultures are positive in only a minority of cases. Endocarditis and meningitis are rare in the antibiotic era.  |
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