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Infectious Disease and Microbiology – Appendicitis
Appendicitis is inflammation of the appendix and is one of the most common surgical emergencies. When the blood supply to the appendix becomes compromised, the condition is termed gangrenous appendicitis. If the inflamed appendix ruptures, it is referred to as perforating appendicitis. When luminal obstruction is the precipitating factor, the condition is described as obstructive appendicitis.
Appendectomy remains the most frequent indication for abdominal surgery. In the United States, at least 250,000 cases of appendicitis occur annually, accounting for more than one million inpatient hospital days. Interestingly, the appendix is found to be normal in up to one-third of patients undergoing emergency appendectomy. Missed appendicitis is among the most common causes of successful malpractice claims against emergency department physicians. Males are affected slightly more often than females, with a male-to-female ratio of approximately 3:2. The lifetime risk is about 8.5% in men and 6.7% in women. Although appendicitis can occur at any age, peak incidence is in the second and third decades of life. Perforation is more common in infants and elderly patients.
The pathogenesis typically begins with luminal obstruction, most commonly caused by a fecalith. Other causes include foreign bodies, lymphoid hyperplasia (often associated with viral infections such as measles), parasitic worms, or tumors such as carcinoid or carcinoma. Obstruction leads to accumulation of mucus, bacterial overgrowth, and invasion of the appendiceal wall. Rising intraluminal pressure causes venous congestion, arterial compromise, ischemia, gangrene, and ultimately perforation. Ruptured appendiceal abscesses may form fistulas. Occasionally, appendicitis may be the first manifestation of Crohn’s disease, and in rare cases, recurrent acute appendicitis can occur with complete resolution between episodes.
Microbiologically, overgrowth of gastrointestinal flora occurs within the obstructed appendix. Common organisms include Escherichia coli, Bacteroides fragilis, Peptostreptococcus, Enterobacteriaceae, and viridans streptococci. Chronic infections due to tuberculosis, amebiasis, or actinomycosis are rare but documented causes.
Clinically, appendicitis classically begins with poorly localized, colicky periumbilical or epigastric pain due to visceral inflammation. As inflammation extends to the parietal peritoneum, pain becomes steady, more severe, and localized to the right lower quadrant at McBurney’s point. Movement and coughing aggravate the pain. Anorexia is common, and its absence should prompt reconsideration of the diagnosis. Nausea and vomiting occur in about half of patients, but vomiting rarely precedes pain. Urinary frequency or dysuria may occur if the inflamed appendix lies near the bladder.
Physical examination findings evolve with disease progression. Right lower quadrant tenderness eventually develops. Guarding, rebound tenderness, and percussion tenderness reflect peritoneal irritation. Rovsing’s sign refers to right lower quadrant pain elicited by palpation of the left lower quadrant. The psoas sign (pain with passive right hip extension) and obturator sign (pain with internal rotation of the flexed right hip) suggest retrocecal or pelvic appendiceal position. Fever is usually mild; temperatures above 38.3°C suggest perforation. A palpable right lower quadrant mass may indicate abscess formation or, less commonly, malignancy.
Laboratory evaluation commonly reveals leukocytosis between 10,000 and 18,000 cells/mm³ with a left shift, though normal white blood cell counts do not exclude appendicitis. Pregnancy testing is essential in women of childbearing age. Imaging plays a critical role in diagnosis. Computed tomography (CT) has an accuracy greater than 90% and improves resource utilization. Ultrasound is particularly useful in children and women of reproductive age to exclude gynecologic pathology. However, normal imaging should not override a convincing clinical picture.
The primary treatment is prompt surgical removal of the appendix. Preoperative antibiotics targeting gram-negative aerobes and anaerobes are standard. Regimens may include beta-lactam/beta-lactamase inhibitor combinations, ceftriaxone plus metronidazole, fluoroquinolone plus metronidazole, or carbapenems. Both laparoscopic and open appendectomy are acceptable approaches. Laparoscopic surgery is associated with less postoperative pain and fewer wound infections, though slightly higher rates of intra-abdominal abscess and increased cost.
In cases where a palpable mass develops several days after symptom onset, suggesting phlegmon formation, surgery may be delayed. These patients are managed with broad-spectrum antibiotics, intravenous fluids, and rest, with interval appendectomy performed approximately three months later unless clinical deterioration necessitates earlier intervention.
Prognosis is generally excellent, with mortality rates less than 1 per 100,000 in developed countries. However, perforated appendicitis carries a mortality rate of approximately 3%, rising to 15% in elderly patients. Delayed diagnosis increases the risk of perforation, which significantly raises postoperative complication rates, including intra-abdominal abscess, peritonitis, and wound infection. Rare complications include portal vein thrombophlebitis and pyogenic liver abscess. Early recognition and timely surgical management remain essential to prevent morbidity and mortality.
Appendicitis is inflammation of the appendix and is one of the most common surgical emergencies. When the blood supply to the appendix becomes compromised, the condition is termed gangrenous appendicitis. If the inflamed appendix ruptures, it is referred to as perforating appendicitis. When luminal obstruction is the precipitating factor, the condition is described as obstructive appendicitis.
Appendectomy remains the most frequent indication for abdominal surgery. In the United States, at least 250,000 cases of appendicitis occur annually, accounting for more than one million inpatient hospital days. Interestingly, the appendix is found to be normal in up to one-third of patients undergoing emergency appendectomy. Missed appendicitis is among the most common causes of successful malpractice claims against emergency department physicians. Males are affected slightly more often than females, with a male-to-female ratio of approximately 3:2. The lifetime risk is about 8.5% in men and 6.7% in women. Although appendicitis can occur at any age, peak incidence is in the second and third decades of life. Perforation is more common in infants and elderly patients.
The pathogenesis typically begins with luminal obstruction, most commonly caused by a fecalith. Other causes include foreign bodies, lymphoid hyperplasia (often associated with viral infections such as measles), parasitic worms, or tumors such as carcinoid or carcinoma. Obstruction leads to accumulation of mucus, bacterial overgrowth, and invasion of the appendiceal wall. Rising intraluminal pressure causes venous congestion, arterial compromise, ischemia, gangrene, and ultimately perforation. Ruptured appendiceal abscesses may form fistulas. Occasionally, appendicitis may be the first manifestation of Crohn’s disease, and in rare cases, recurrent acute appendicitis can occur with complete resolution between episodes.
Microbiologically, overgrowth of gastrointestinal flora occurs within the obstructed appendix. Common organisms include Escherichia coli, Bacteroides fragilis, Peptostreptococcus, Enterobacteriaceae, and viridans streptococci. Chronic infections due to tuberculosis, amebiasis, or actinomycosis are rare but documented causes.
Clinically, appendicitis classically begins with poorly localized, colicky periumbilical or epigastric pain due to visceral inflammation. As inflammation extends to the parietal peritoneum, pain becomes steady, more severe, and localized to the right lower quadrant at McBurney’s point. Movement and coughing aggravate the pain. Anorexia is common, and its absence should prompt reconsideration of the diagnosis. Nausea and vomiting occur in about half of patients, but vomiting rarely precedes pain. Urinary frequency or dysuria may occur if the inflamed appendix lies near the bladder.
Physical examination findings evolve with disease progression. Right lower quadrant tenderness eventually develops. Guarding, rebound tenderness, and percussion tenderness reflect peritoneal irritation. Rovsing’s sign refers to right lower quadrant pain elicited by palpation of the left lower quadrant. The psoas sign (pain with passive right hip extension) and obturator sign (pain with internal rotation of the flexed right hip) suggest retrocecal or pelvic appendiceal position. Fever is usually mild; temperatures above 38.3°C suggest perforation. A palpable right lower quadrant mass may indicate abscess formation or, less commonly, malignancy.
Laboratory evaluation commonly reveals leukocytosis between 10,000 and 18,000 cells/mm³ with a left shift, though normal white blood cell counts do not exclude appendicitis. Pregnancy testing is essential in women of childbearing age. Imaging plays a critical role in diagnosis. Computed tomography (CT) has an accuracy greater than 90% and improves resource utilization. Ultrasound is particularly useful in children and women of reproductive age to exclude gynecologic pathology. However, normal imaging should not override a convincing clinical picture.
The primary treatment is prompt surgical removal of the appendix. Preoperative antibiotics targeting gram-negative aerobes and anaerobes are standard. Regimens may include beta-lactam/beta-lactamase inhibitor combinations, ceftriaxone plus metronidazole, fluoroquinolone plus metronidazole, or carbapenems. Both laparoscopic and open appendectomy are acceptable approaches. Laparoscopic surgery is associated with less postoperative pain and fewer wound infections, though slightly higher rates of intra-abdominal abscess and increased cost.
In cases where a palpable mass develops several days after symptom onset, suggesting phlegmon formation, surgery may be delayed. These patients are managed with broad-spectrum antibiotics, intravenous fluids, and rest, with interval appendectomy performed approximately three months later unless clinical deterioration necessitates earlier intervention.
Prognosis is generally excellent, with mortality rates less than 1 per 100,000 in developed countries. However, perforated appendicitis carries a mortality rate of approximately 3%, rising to 15% in elderly patients. Delayed diagnosis increases the risk of perforation, which significantly raises postoperative complication rates, including intra-abdominal abscess, peritonitis, and wound infection. Rare complications include portal vein thrombophlebitis and pyogenic liver abscess. Early recognition and timely surgical management remain essential to prevent morbidity and mortality.
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