A 49-year-old man with a history of untreated hepatitis B viral infection and known hepati… — USMLE Step 2 CK

A 49-year-old man with a history of untreated hepatitis B viral infection and known hepatic cirrhosis is brought to the emergency department via ambulance due to the abrupt onset of excruciating, diffuse abdominal pain that began 4 hours ago. He is lethargic and confused. His temperature is $39.2^\circ\text{C}$ ( $102.6^\circ\text{F}$ ), blood pressure is $72/45\text{ mmHg}$ , pulse is $130/\text{min}$ , and respiratory rate is $28/\text{min}$ . Pulse oximetry shows $92\%$ on room air. Physical examination reveals a markedly distended abdomen with board-like rigidity, severe diffuse tenderness, and rebound tenderness. Bowel sounds are absent. Skin examination shows numerous spider telangiectasias. Laboratory studies reveal a leukocyte count of $18,500/\text{mm}^3$ , hemoglobin of $10.8\text{ g/dL}$ , platelet count of $72,000/\text{mm}^3$ , and creatinine of $2.4\text{ mg/dL}$ . Arterial blood gas on room air shows a pH of $7.22$ , pCO2 of $30\text{ mmHg}$ , and pO2 of $68\text{ mmHg}$ . A bedside diagnostic paracentesis yields cloudy ascitic fluid with a leukocyte count of $8,200/\text{mm}^3$ ( $90\%$ neutrophils), total protein of $2.8\text{ g/dL}$ , glucose of $22\text{ mg/dL}$ , and lactate dehydrogenase (LDH) of $640\text{ U/L}$ (Serum LDH upper limit: $220\text{ U/L}$ ). Gram stain shows many polymorphonuclear leukocytes, abundant gram-negative bacilli, and gram-positive cocci. Which of the following is the most appropriate next step in management?

Administration of intravenous piperacillin-tazobactam and emergent exploratory laparotomyAnswer
B
Administration of intravenous ceftriaxone and albumin, followed by admission to the medical intensive care unit
C
Transport to the radiology suite for an urgent computed tomography scan of the abdomen and pelvis
D
Placement of a nasogastric tube, aggressive intravenous fluid resuscitation, and serial abdominal examinations
E
Administration of intravenous sodium bicarbonate and urgent preparation for continuous venovenous hemofiltration

Answer

Administration of intravenous piperacillin-tazobactam and emergent exploratory laparotomy

The patient's presentation of a rigid abdomen and septic shock strongly suggests a surgical emergency. The ascitic fluid analysis confirms secondary bacterial peritonitis, as it meets Runyon criteria (protein

>1\text{ g/dL}

, glucose

<50\text{ mg/dL}

, fluid LDH elevated above the serum upper limit of normal) and demonstrates a polymicrobial Gram stain. Unlike spontaneous bacterial peritonitis (SBP), which is treated medically, secondary peritonitis is caused by a perforated viscus or localized abscess and requires urgent surgical source control. Furthermore, because the patient is hemodynamically unstable, it is unsafe to transport him to the radiology suite for a CT scan. The most appropriate next step is the administration of broad-spectrum antibiotics that cover anaerobes and Enterococcus (such as piperacillin-tazobactam) followed by emergent exploratory laparotomy.

Step-by-Step Solution

Analyze the patient's clinical presentation and vital signs.

The patient has a rigid, surgical abdomen with rebound tenderness, accompanied by severe hemodynamic instability (blood pressure

72/45\text{ mmHg}

, pulse

130/\text{min}

) indicating septic shock.

Identifying shock and a surgical abdomen dictates the urgency of intervention and precludes delaying for definitive imaging.

Evaluate the ascitic fluid analysis to differentiate between spontaneous (SBP) and secondary bacterial peritonitis.

The fluid has

>250

neutrophils/mm

^3

, protein

>1\text{ g/dL}

, glucose

<50\text{ mg/dL}

, LDH greater than the serum upper limit, and a polymicrobial Gram stain.

These findings fulfill Runyon's criteria for secondary bacterial peritonitis (e.g., from a perforated viscus), which has a fundamentally different management strategy than SBP.

Determine the appropriate therapeutic approach for secondary bacterial peritonitis in an unstable patient.

The patient requires broad-spectrum intravenous antibiotics (e.g., piperacillin-tazobactam) and emergent exploratory laparotomy.

Secondary peritonitis is uniformly fatal without surgical source control. Because the patient is hemodynamically unstable, transporting him to the CT scanner is unsafe; he must go directly to the operating room.

Key Concept

Secondary bacterial peritonitis is distinguished from spontaneous bacterial peritonitis by ascitic fluid meeting at least two Runyon criteria (protein

>1\text{ g/dL}

, glucose

<50\text{ mg/dL}

, LDH

>

serum upper limit) and a polymicrobial Gram stain. Hemodynamically unstable patients with secondary peritonitis require broad-spectrum antibiotics and emergent exploratory laparotomy without delaying for CT imaging.

Estimated Time:1m 30s

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