A 40-year-old man presents with acute abdominal pain. Past medical history is significant for hepatitis C, complicated by multiple recent visits with associated ascites. His temperature is 38.3°C (100.9°F), heart rate is 115/min, blood pressure is 88/48 mm Hg, and respiratory rate is 16/min. On physical examination, the patient is alert and in moderate discomfort. Cardiopulmonary examination is unremarkable. Abdominal examination reveals distant bowel sounds on auscultation. There is also mild diffuse abdominal tenderness to palpation with guarding present. The remainder of the physical examination is unremarkable. A paracentesis is performed. Laboratory results are significant for the following: Leukocyte count 11,630/µL (with 94% neutrophils) Platelets 24,000/µL Hematocrit 29% Ascitic fluid analysis: Cell count 658 PMNs/µL Total protein 1.2 g/dL Glucose 24 mg/dL Gram stain Gram-negative rods Culture Culture yields growth of E. coli Which of the following is the next, best step in the management of this patient?

Abdominal radiography and contrast CT of the abdomen

Intravenous fluid resuscitation

A 49-year-old woman with a history of hepatitis C cirrhosis complicated by esophageal varices, ascites, and hepatic encephalopathy presents with 1 week of increasing abdominal discomfort. Currently, she takes lactulose, rifaximin, furosemide, and spironolactone. On physical examination, she has mild asterixis, generalized jaundice, and a distended abdomen with positive fluid wave. Diagnostic paracentesis yields a WBC count of 1196/uL with 85% neutrophils. Which of the following is the most appropriate treatment?

Transjugular intrahepatic portosystemic shunt placement

Large volume paracentesis with albumin

Increased furosemide and spironolactone

A 56-year-old male with a history of hepatitis C cirrhosis status post TIPS procedure is brought in by his wife to the emergency department because he has been acting disoriented, slurring his speech, and sleeping throughout the day. On arrival the patient is afebrile and his vital signs are pulse is 87/min, blood pressure is 137/93 mmHg, and respirations are 12/min with shallow breaths. Examination reveals a jaundiced male who appears older than stated age. Abdominal exam is positive for a fluid wave and shifting dullness to percussion. You note enlarged breasts, decreased facial hair, 3+ patellar reflexes bilaterally, and the following in the upper extremity (Image A). Paracentesis reveals ascitic fluid with neutrophil counts of < 100 cells/mcL. Serum creatinine is 1.0 and BUN is 15. Which of the following is the next best step in management?

Administer neomycin and glucose

IV albumin and antibiotic therapy with cefotaxime

Administer rifaximin and glucose

A 52-year-old man, with a history of alcoholism, presents with loss of appetite, abdominal pain, and fever for the past 24 hours. He says he consumed 12 beers and a bottle of vodka 2 days ago. He reports a 19-year history of alcoholism. His blood pressure is 100/70 mm Hg, pulse is 100/min, respirations are 20/min, and oxygen saturation is 99% on room air. Laboratory findings are significant for the following: Sodium 137 mEq/L Potassium 3.4 mEq/L Alanine aminotransferase (ALT) 230 U/L Aspartate aminotransferase (AST) 470 U/L Which of the following histopathologic findings would most likely be found on a liver biopsy of this patient?

Cytoplasmic inclusion bodies with keratin

Positive periodic acid-Schiff stain

A 25-year-old woman presents to her primary care physician complaining of several months of diarrhea. She has also had crampy abdominal pain. She has tried modifying her diet without improvement. She has many watery, non-bloody bowel movements per day. She also reports feeling fatigued. The patient has not recently traveled outside of the country. She has lost 10 pounds since her visit last year, and her BMI is now 20. On exam, she has skin tags and an anal fissure. Which of the following would most likely be seen on endoscopy and biopsy?

Focal ulcerations with granuloma

Diffuse, non-focal ulcerations with granuloma

Diffuse, non-focal ulcerations without granuloma

Pseudopolyps and continuous mucosal involvement

Friable mucosa with pinpoint hemorrhages

A 65-year-old man is brought to the emergency department because of a 1-day history of fever and disorientation. His wife reports that he had abdominal pain and diarrhea the previous day. He drinks 60 oz of alcohol weekly. His pulse is 110/min and blood pressure is 96/58 mm Hg. Examination shows jaundice, palmar erythema, spider nevi on his chest, dilated veins on the anterior abdominal wall, and 2+ edema of the lower extremities. The abdomen is soft and diffusely tender; there is shifting dullness to percussion. His albumin is 1.4 g/dL, bilirubin is 5 mg/dL, and prothrombin time is 31 seconds (INR = 3.3). Hepatitis serology is negative. A CT scan of the abdomen is shown. Which of the following processes is the most likely explanation for these findings?

Fibrous bands surrounding regenerating hepatocytes

Accumulation of iron in hepatocytes

Ground-glass hepatocytes with cytotoxic T cells

Misfolded protein aggregates in hepatocellular endoplasmic reticulum

Hepatocyte swelling with Councilman bodies and monocyte infiltration

An esophageal biopsy sample from a 47-year-old male with chronic heartburn reveals intestinal metaplasia. Which of the following abnormal cell types is likely present in this patient's esophagus?

Keratinized stratified squamous epithelium

Pseudostratified ciliated columnar epithelium

A 21-year-old man comes to the physician because of a 6-month history of severe abdominal pain, bloating, and episodic diarrhea. He has also had a 5-kg (11-lb) weight loss during this time. Physical examination shows a mildly distended abdomen, hyperactive bowel sounds, and diffuse abdominal tenderness. A biopsy specimen of the colonic mucosa shows scattered areas of inflammation with fibrosis and noncaseating granulomas. Which of the following is most likely involved in the pathogenesis of this patient's condition?

Increased activity of type 1 T helper cells

Viral infection with intranuclear inclusions

Intestinal overgrowth of toxigenic bacteria

Accumulation of intracellular bacteria in macrophages

Peritonitis for USMLE Step 2 CK: High-Yield Pathology Lessons

Peritonitis - Belly on Fire

Inflammation of the peritoneum, the silk-like membrane lining the abdominal wall.
Types
- Spontaneous Bacterial Peritonitis (SBP): Infection of ascitic fluid, usually from cirrhosis. No evident source.
  - Dx: Ascitic fluid PMN > 250 cells/mm³.
  - Common bugs: E. coli, Klebsiella, Strep pneumo.
- Secondary Peritonitis: Due to perforation of a viscus (e.g., appendix, ulcer).
  - Polymicrobial infection is common.
Clinical Features
- Fever, abdominal pain, guarding, rebound tenderness.
- Classic sign: Board-like rigidity.

⭐ High-Yield: In a patient with cirrhosis, ascites, and fever, a paracentesis showing a neutrophil count (PMN) of > 250/mm³ is diagnostic for SBP.

Guarding and Rebound Tenderness in Peritonitis

SBP - Cirrhosis's Sneaky Friend

Paracentesis procedure for peritonitis diagnosis

Definition: Bacterial infection of ascitic fluid without an evident intra-abdominal source, common in advanced cirrhosis.
Etiology: Primarily monomicrobial. Gram-negative bacilli are most frequent, especially E. coli (~70%), Klebsiella, and Streptococcus species.
Clinical: Can be subtle. Look for fever, abdominal pain, and altered mental status (worsening hepatic encephalopathy).
Diagnosis: Requires paracentesis. Key finding is an ascitic fluid absolute neutrophil count (PMN) $≥ \textbf{250}/mm^3$.
Management:
- Empiric antibiotics (e.g., 3rd-gen cephalosporin like cefotaxime).
- IV albumin infusion.

⭐ High-Yield: Initiate treatment based on a PMN count $≥ \textbf{250}/mm^3$ alone. Do not wait for culture results, as they have low sensitivity and delay can be fatal.

Secondary Peritonitis - The Great Escape

Pathophysiology: Breach of GI/GU tract integrity → spillage of polymicrobial gut flora into the normally sterile peritoneal cavity.
Common Causes: Perforated peptic ulcer, acute appendicitis, diverticulitis, trauma, or iatrogenic injury.
Microbiology: Mixed aerobes (E. coli, Klebsiella) and anaerobes (Bacteroides fragilis).
Diagnosis: Clinical signs of an acute abdomen (rebound tenderness, guarding). Upright CXR or CT scan confirms pneumoperitoneum (free air).

⭐ Bacteroides fragilis is the most common anaerobe isolated, mandating antibiotic coverage for anaerobes.

Upright CXR: Free subdiaphragmatic air (pneumoperitoneum)

Dx & Tx - Find It, Fix It

Find It (Diagnosis):
- Labs: CBC (↑ WBC), blood cultures.
- Paracentesis (if ascites): Ascitic fluid PMN count > 250 cells/mm³ is diagnostic for SBP.
- Imaging: Upright X-ray (free air) or CT scan (abscess, definitive source).
Fix It (Treatment Algorithm):

⭐ For Spontaneous Bacterial Peritonitis (SBP), treatment is empiric antibiotics (e.g., 3rd-gen cephalosporin). Surgical intervention is typically NOT indicated, unlike secondary peritonitis.

High‑Yield Points - ⚡ Biggest Takeaways

Spontaneous Bacterial Peritonitis (SBP) is a key complication of cirrhosis and ascites, most commonly caused by E. coli. Diagnosis requires >250 neutrophils/mm³ in ascitic fluid.

Secondary peritonitis results from bowel perforation (e.g., appendicitis, diverticulitis) and is typically polymicrobial.

Peritoneal dialysis (PD)-associated peritonitis is often caused by skin flora like Staph aureus.

Classic signs include diffuse abdominal pain, rebound tenderness, and guarding.

Tuberculous peritonitis can present insidiously with a "doughy" abdomen and high ascitic fluid ADA.

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Peritonitis