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Infectious Diseases and Microbiology: Abdominal Pain and Fever
Basics
Description and Definition
This topic reviews conditions in which fever occurs together with abdominal pain.
Approach to the Patient
The initial priority is deciding whether the presentation represents a surgical emergency. Life-threatening diagnoses must be rapidly excluded, and clinicians should remember that pain referred from extra-abdominal sites can mimic primary abdominal disease. Severe intraabdominal infections may present with minimal or atypical findings, particularly in neonates, older adults, and immunocompromised patients. Rapid assessment of symptom onset, severity, and character is essential, along with immediate vital sign evaluation and a comprehensive physical examination. Beyond a careful abdominal exam, full systemic assessment is required, especially of the cardiopulmonary systems. Rectal examination should generally be performed, except in patients with severe neutropenia, in whom careful inspection is preferred.
Epidemiology
Appendicitis commonly presents to emergency departments with fever and abdominal pain. In the United States, most typhoid fever cases are acquired during travel, particularly to Mexico, India, and Pakistan. Travel to tropical regions raises concern for malaria, while travel to areas endemic for louse-borne relapsing fever such as Ethiopia, parts of South America, and East Asia suggests Borrelia recurrentis. HIV infection can produce fever and abdominal pain through multiple mechanisms and should be considered in individuals with risk factors or from high-prevalence regions such as sub-Saharan Africa and Southeast Asia, including those with intravenous drug exposure. Intestinal tuberculosis is associated with ingestion of unpasteurized dairy products, malnutrition, and HIV. Animal exposure may indicate leptospirosis, toxoplasmosis, brucellosis, or Q fever. Other vectors are linked to dengue fever, typhus, and psittacosis. Individuals with sickle cell disease or prior splenectomy are predisposed to salmonellosis. Melena, positive fecal occult blood tests, and weight loss should prompt consideration of solid tumors or lymphoma. Cardiovascular disease, the leading cause of mortality in Western countries, may frequently present with abdominal pain.
Etiology
Diffuse abdominal pain with fever suggests peritonitis, ileus or obstruction, mesenteric ischemia, ruptured aneurysm, or metabolic disorders. Infectious causes vary by location: right upper quadrant pain may result from acute cholecystitis including perforation, hepatitis, Fitz-Hugh–Curtis syndrome, pyelonephritis, pneumonia, or liver abscess; left upper quadrant pain from pyelonephritis, pneumonia, or splenic abscess; epigastric pain from diverticulitis, early appendicitis, primary or secondary peritonitis including tuberculous forms, acute gastroenteritis, pancreatitis, cholangitis, inflammatory bowel disease, Clostridioides difficile colitis, or mediastinitis; right lower quadrant pain from appendicitis, salpingitis, psoas abscess, mesenteric adenitis, pelvic inflammatory disease, or bowel perforation; left lower quadrant pain from diverticulitis, salpingitis, psoas abscess, mesenteric adenitis, pelvic infection, or bowel perforation. Noninfectious causes include acute porphyria, adrenal crisis, systemic inflammatory and granulomatous disorders, diabetic ketoacidosis, esophageal disease, familial Mediterranean fever, lead poisoning, intraabdominal or hematologic malignancy, mediastinal tumors, mesenteric ischemia or thrombosis, myocardial infarction, pancreatitis, pneumothorax complicating pneumonia, pulmonary embolism, ruptured ovarian follicle, and sickle cell crisis. Enteric fever presents with fever and abdominal pain and may include headache, hepatosplenomegaly, and a macular rash known as rose spots. Typhoid fever caused by Salmonella typhi is the classic example, but similar syndromes can result from Salmonella paratyphi and numerous bacterial, rickettsial, viral, fungal, and parasitic pathogens. Mesenteric adenitis often mimics appendicitis and is usually viral or due to Yersinia enterocolitica. Eosinophilia with abdominal cramps or diarrhea and fever suggests helminthic infection or intestinal lymphoma. Enterohemorrhagic Escherichia coli infections typically cause crampy pain before bloody diarrhea and are often afebrile. In patients with HIV, both typical causes seen in immunocompetent hosts and additional conditions such as typhlitis, bowel perforation with abscess, HIV-related cholangiopathy, hepatic abscesses, bacillary angiomatosis, pancreatitis, splenic infarction or abscess, gastrointestinal tuberculosis, cytomegalovirus disease, fungal and mycobacterial infections, parasitic enteritis, Giardia, Strongyloides, Kaposi sarcoma, and lymphoma must be considered.
Diagnosis
History
Assessment should include pain location, intensity, quality, radiation, aggravating and relieving factors, relation to meals, bowel habits, recent travel, dietary and animal exposures, and cardiovascular risk factors.
Physical Examination
Evaluation includes bowel sounds and abdominal bruits, localization and severity of tenderness, and palpation for hepatosplenomegaly. Signs of acute or chronic liver disease such as jaundice, scleral icterus, spider angiomata, clubbing, and ascites should be sought. The oropharynx and anus should be examined for lesions. Relative bradycardia supports enteric fever, which may also present with conjunctivitis, pharyngitis, or pulmonary findings. Acute diarrhea with sterile arthritis suggests Yersinia infection. Right lower quadrant rebound tenderness may reflect mesenteric adenitis, and only about half of appendicitis cases show classic migratory pain.
Diagnostic Tests and Interpretation
Laboratory Studies
Recommended tests include complete blood count with differential, electrolytes, renal function, liver enzymes and function tests, and calcium. Blood cultures should be obtained before empiric antibiotics, along with urine culture and electrocardiography. Blood, stool, and urine cultures are required in suspected enteric fever prior to therapy, with bone marrow cultures considered if blood cultures are negative and typhoid fever is suspected. Widal testing has limited diagnostic value outside Salmonella typhi. Leukopenia is common in typhoid fever. Eosinophilia warrants stool examination for ova and parasites. Fever is uncommon in giardiasis, occurring in a minority of cases, and diagnosis may require stool studies, small-bowel biopsy, or immunoassays. Malaria evaluation requires thick and thin blood smears every 24 hours for three sets, with rapid tests as adjuncts. Stool testing should be guided by context and include evaluation for C. difficile, ova and parasites, and bacterial cultures for major enteric pathogens. Most appendicitis cases demonstrate leukocytosis.
Imaging
Plain abdominal radiographs may reveal free air, loss of psoas shadow, or radiopaque calculi, but ultrasonography or computed tomography is often required. Ultrasound is the preferred initial test for suspected biliary or renal infection but is limited for deep structures and postoperative evaluation. CT imaging offers higher diagnostic accuracy, especially with contrast, though renal toxicity must be considered. Ultrasound is standard for initial assessment of biliary disease, while endoscopic ultrasonography provides very high accuracy for bile duct stones. Magnetic resonance cholangiography offers a noninvasive alternative for biliary imaging. Acute acalculous cholecystitis accounts for a minority of cases, and nuclear scanning is rarely first line but may be useful in selected situations. Endoscopic retrograde, percutaneous transhepatic, and intraoperative cholangiography are highly accurate for common bile duct stones but are invasive and carry complication risks.
Treatment
Medications
Empiric antimicrobial therapy is often required before a definitive diagnosis is established and should be tailored to the suspected infectious syndrome and travel history. Mesenteric adenitis is typically self-limited and may not require antibiotics, though trimethoprim-sulfamethoxazole, third-generation cephalosporins, or fluoroquinolones can be used when indicated. Mild to moderate community-acquired intraabdominal infections such as acute cholecystitis can be treated with a fluoroquinolone plus metronidazole or a beta-lactam/beta-lactamase inhibitor. Vancomycin is added when methicillin-resistant Staphylococcus aureus is suspected, while ampicillin is preferred for susceptible Enterococcus species. Severe community-acquired or health-care–associated intraabdominal infections require early broad-spectrum multidrug regimens targeting nosocomial organisms, often including antipseudomonal cephalosporins or carbapenems.
Ongoing Care and Follow-Up
Clinicians should remain alert for subtle or atypical presentations in neonates, infants, and older adults. Patients require close observation until fever resolves. Persistent unexplained fever and abdominal pain should prompt consideration of abdominal CT imaging when history, examination, and ultrasound are nondiagnostic.
Basics
Description and Definition
This topic reviews conditions in which fever occurs together with abdominal pain.
Approach to the Patient
The initial priority is deciding whether the presentation represents a surgical emergency. Life-threatening diagnoses must be rapidly excluded, and clinicians should remember that pain referred from extra-abdominal sites can mimic primary abdominal disease. Severe intraabdominal infections may present with minimal or atypical findings, particularly in neonates, older adults, and immunocompromised patients. Rapid assessment of symptom onset, severity, and character is essential, along with immediate vital sign evaluation and a comprehensive physical examination. Beyond a careful abdominal exam, full systemic assessment is required, especially of the cardiopulmonary systems. Rectal examination should generally be performed, except in patients with severe neutropenia, in whom careful inspection is preferred.
Epidemiology
Appendicitis commonly presents to emergency departments with fever and abdominal pain. In the United States, most typhoid fever cases are acquired during travel, particularly to Mexico, India, and Pakistan. Travel to tropical regions raises concern for malaria, while travel to areas endemic for louse-borne relapsing fever such as Ethiopia, parts of South America, and East Asia suggests Borrelia recurrentis. HIV infection can produce fever and abdominal pain through multiple mechanisms and should be considered in individuals with risk factors or from high-prevalence regions such as sub-Saharan Africa and Southeast Asia, including those with intravenous drug exposure. Intestinal tuberculosis is associated with ingestion of unpasteurized dairy products, malnutrition, and HIV. Animal exposure may indicate leptospirosis, toxoplasmosis, brucellosis, or Q fever. Other vectors are linked to dengue fever, typhus, and psittacosis. Individuals with sickle cell disease or prior splenectomy are predisposed to salmonellosis. Melena, positive fecal occult blood tests, and weight loss should prompt consideration of solid tumors or lymphoma. Cardiovascular disease, the leading cause of mortality in Western countries, may frequently present with abdominal pain.
Etiology
Diffuse abdominal pain with fever suggests peritonitis, ileus or obstruction, mesenteric ischemia, ruptured aneurysm, or metabolic disorders. Infectious causes vary by location: right upper quadrant pain may result from acute cholecystitis including perforation, hepatitis, Fitz-Hugh–Curtis syndrome, pyelonephritis, pneumonia, or liver abscess; left upper quadrant pain from pyelonephritis, pneumonia, or splenic abscess; epigastric pain from diverticulitis, early appendicitis, primary or secondary peritonitis including tuberculous forms, acute gastroenteritis, pancreatitis, cholangitis, inflammatory bowel disease, Clostridioides difficile colitis, or mediastinitis; right lower quadrant pain from appendicitis, salpingitis, psoas abscess, mesenteric adenitis, pelvic inflammatory disease, or bowel perforation; left lower quadrant pain from diverticulitis, salpingitis, psoas abscess, mesenteric adenitis, pelvic infection, or bowel perforation. Noninfectious causes include acute porphyria, adrenal crisis, systemic inflammatory and granulomatous disorders, diabetic ketoacidosis, esophageal disease, familial Mediterranean fever, lead poisoning, intraabdominal or hematologic malignancy, mediastinal tumors, mesenteric ischemia or thrombosis, myocardial infarction, pancreatitis, pneumothorax complicating pneumonia, pulmonary embolism, ruptured ovarian follicle, and sickle cell crisis. Enteric fever presents with fever and abdominal pain and may include headache, hepatosplenomegaly, and a macular rash known as rose spots. Typhoid fever caused by Salmonella typhi is the classic example, but similar syndromes can result from Salmonella paratyphi and numerous bacterial, rickettsial, viral, fungal, and parasitic pathogens. Mesenteric adenitis often mimics appendicitis and is usually viral or due to Yersinia enterocolitica. Eosinophilia with abdominal cramps or diarrhea and fever suggests helminthic infection or intestinal lymphoma. Enterohemorrhagic Escherichia coli infections typically cause crampy pain before bloody diarrhea and are often afebrile. In patients with HIV, both typical causes seen in immunocompetent hosts and additional conditions such as typhlitis, bowel perforation with abscess, HIV-related cholangiopathy, hepatic abscesses, bacillary angiomatosis, pancreatitis, splenic infarction or abscess, gastrointestinal tuberculosis, cytomegalovirus disease, fungal and mycobacterial infections, parasitic enteritis, Giardia, Strongyloides, Kaposi sarcoma, and lymphoma must be considered.
Diagnosis
History
Assessment should include pain location, intensity, quality, radiation, aggravating and relieving factors, relation to meals, bowel habits, recent travel, dietary and animal exposures, and cardiovascular risk factors.
Physical Examination
Evaluation includes bowel sounds and abdominal bruits, localization and severity of tenderness, and palpation for hepatosplenomegaly. Signs of acute or chronic liver disease such as jaundice, scleral icterus, spider angiomata, clubbing, and ascites should be sought. The oropharynx and anus should be examined for lesions. Relative bradycardia supports enteric fever, which may also present with conjunctivitis, pharyngitis, or pulmonary findings. Acute diarrhea with sterile arthritis suggests Yersinia infection. Right lower quadrant rebound tenderness may reflect mesenteric adenitis, and only about half of appendicitis cases show classic migratory pain.
Diagnostic Tests and Interpretation
Laboratory Studies
Recommended tests include complete blood count with differential, electrolytes, renal function, liver enzymes and function tests, and calcium. Blood cultures should be obtained before empiric antibiotics, along with urine culture and electrocardiography. Blood, stool, and urine cultures are required in suspected enteric fever prior to therapy, with bone marrow cultures considered if blood cultures are negative and typhoid fever is suspected. Widal testing has limited diagnostic value outside Salmonella typhi. Leukopenia is common in typhoid fever. Eosinophilia warrants stool examination for ova and parasites. Fever is uncommon in giardiasis, occurring in a minority of cases, and diagnosis may require stool studies, small-bowel biopsy, or immunoassays. Malaria evaluation requires thick and thin blood smears every 24 hours for three sets, with rapid tests as adjuncts. Stool testing should be guided by context and include evaluation for C. difficile, ova and parasites, and bacterial cultures for major enteric pathogens. Most appendicitis cases demonstrate leukocytosis.
Imaging
Plain abdominal radiographs may reveal free air, loss of psoas shadow, or radiopaque calculi, but ultrasonography or computed tomography is often required. Ultrasound is the preferred initial test for suspected biliary or renal infection but is limited for deep structures and postoperative evaluation. CT imaging offers higher diagnostic accuracy, especially with contrast, though renal toxicity must be considered. Ultrasound is standard for initial assessment of biliary disease, while endoscopic ultrasonography provides very high accuracy for bile duct stones. Magnetic resonance cholangiography offers a noninvasive alternative for biliary imaging. Acute acalculous cholecystitis accounts for a minority of cases, and nuclear scanning is rarely first line but may be useful in selected situations. Endoscopic retrograde, percutaneous transhepatic, and intraoperative cholangiography are highly accurate for common bile duct stones but are invasive and carry complication risks.
Treatment
Medications
Empiric antimicrobial therapy is often required before a definitive diagnosis is established and should be tailored to the suspected infectious syndrome and travel history. Mesenteric adenitis is typically self-limited and may not require antibiotics, though trimethoprim-sulfamethoxazole, third-generation cephalosporins, or fluoroquinolones can be used when indicated. Mild to moderate community-acquired intraabdominal infections such as acute cholecystitis can be treated with a fluoroquinolone plus metronidazole or a beta-lactam/beta-lactamase inhibitor. Vancomycin is added when methicillin-resistant Staphylococcus aureus is suspected, while ampicillin is preferred for susceptible Enterococcus species. Severe community-acquired or health-care–associated intraabdominal infections require early broad-spectrum multidrug regimens targeting nosocomial organisms, often including antipseudomonal cephalosporins or carbapenems.
Ongoing Care and Follow-Up
Clinicians should remain alert for subtle or atypical presentations in neonates, infants, and older adults. Patients require close observation until fever resolves. Persistent unexplained fever and abdominal pain should prompt consideration of abdominal CT imaging when history, examination, and ultrasound are nondiagnostic.
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