Intra-abdominal abscess

Acute appendicitis is luminal obstruction and infection of the vermiform appendix presenting as migratory periumbilical-to-right-lower-quadrant pain, diagnosed by the classic history and exam plus confirmatory imaging (CT in adults, ultrasound or MRI in children and pregnancy), and treated with prompt appendectomy or, in selected uncomplicated cases, antibiotics alone.

Diverticulitis is inflammation and micro- or macro-perforation of a colonic diverticulum, most often sigmoid, presenting with left lower quadrant pain, fever, and altered bowel habits. CT abdomen and pelvis with contrast confirms the diagnosis, separates uncomplicated from complicated disease, and grades complicated disease by the modified Hinchey classification to guide antibiotics, drainage, or surgery.

Crohn disease is a chronic transmural inflammatory bowel disease that can affect any segment from mouth to anus in skip lesions, most classically the terminal ileum, and is confirmed by ileocolonoscopy showing cobblestoning, skip areas, and non-caseating granulomas on biopsy. Management follows an ordered sequence of glucocorticoid or budesonide induction followed by immunomodulator or biologic maintenance, with surgery reserved for fixed complications rather than cure.

Pelvic inflammatory disease is an ascending polymicrobial infection of the upper female genital tract, most often caused by Neisseria gonorrhoeae, Chlamydia trachomatis, or Mycoplasma genitalium, diagnosed clinically on uterine, adnexal, or cervical motion tenderness. Most women are treated as outpatients with a single dose of ceftriaxone plus 14 days of doxycycline, while parenteral cefotetan or cefoxitin plus doxycycline, or clindamycin plus gentamicin, is reserved for hospitalized patients, with tubo-ovarian abscess and infertility among the major complications of delayed treatment.

A fertilized ovum implants outside the endometrial cavity, almost always in the fallopian tube, and is the leading cause of maternal death in the first trimester. Diagnosis rests on quantitative beta-hCG paired with transvaginal ultrasound, and management branches immediately on hemodynamic stability.

Acute mesenteric ischemia is an abrupt drop in small-bowel blood flow, most often superior mesenteric artery embolism, presenting as severe abdominal pain out of proportion to an unimpressive early examination. CT angiography confirms the diagnosis, and survival depends on immediate resuscitation, antibiotics, and anticoagulation followed by urgent revascularization or resection before infarction and peritonitis develop.

Pyogenic liver abscess is a polymicrobial hepatic infection that most often seeds from the biliary tract or the portal circulation, presenting with fever, right upper quadrant pain, and a cholestatic liver profile. Diagnosis rests on contrast imaging plus culture, and treatment combines empiric broad-spectrum antibiotics with image-guided drainage for abscesses at or above 3 to 5 cm.

Infected pancreatic necrosis is secondary bacterial or fungal infection of devitalized pancreatic or peripancreatic tissue, usually one to four weeks into severe acute pancreatitis. Diagnosis rests on gas within a necrotic collection on CT or a positive culture from image-guided aspiration. First-line treatment is a necrosis-penetrant carbapenem such as meropenem plus staged, minimally invasive drainage using the step-up approach.

Renal abscess is a focal, pus-filled collection in the renal parenchyma (intrarenal) or perinephric space, most often complicating unresolved ascending pyelonephritis with gram-negative organisms or hematogenous staphylococcal seeding. Persistent fever and pyuria despite 5-7 days of appropriate antibiotics should prompt CT or ultrasound imaging, with percutaneous or surgical drainage required for perinephric collections and intrarenal abscesses larger than 5 cm.

Sepsis is life-threatening organ dysfunction caused by a dysregulated host response to infection, identified by an acute rise in SOFA score of 2 points or more in a patient with known or suspected infection. Survival depends on recognizing the pattern early and completing the hour-1 bundle: lactate, blood cultures before antibiotics, broad-spectrum antibiotics such as cefepime 2 g IV every 8 hours, and 30 mL/kg crystalloid for hypotension or a lactate of 4 mmol/L or higher.

Septic shock is the subset of sepsis with hypotension requiring vasopressors to maintain a mean arterial pressure above 65 mm Hg plus a serum lactate above 2 mmol/L despite adequate fluid resuscitation, carrying in-hospital mortality of 40% or higher. Management is a timed sequence: 30 mL/kg crystalloid bolus, blood cultures and broad-spectrum antibiotics within 1 hour, norepinephrine titrated to MAP >=65, and escalation to a second vasopressor and stress-dose hydrocortisone when hypotension persists.