Following a weekend camping trip during which he consumed several undercooked beef patties… — USMLE Step 2 CK

Following a weekend camping trip during which he consumed several undercooked beef patties, a $32$ -year-old male is evaluated in the emergency department due to severe, crampy abdominal pain and frequent episodes of grossly bloody diarrhea. His symptoms began three days ago and have progressively worsened. The patient is otherwise healthy and takes no medications. Vital signs reveal a temperature of $37.1^\circ\text{C}$ ( $98.8^\circ\text{F}$ ), a blood pressure of $122/78\text{ mmHg}$ , and a pulse of $84/\text{min}$ . Physical examination demonstrates a soft, non-distended abdomen with diffuse tenderness, but no rebound guarding or rigidity is appreciated.

The results of laboratory investigations are shown below:

Laboratory Test	Result	Reference Range
Hemoglobin	$14.1\text{ g/dL}$	$13.5-17.5\text{ g/dL}$
Leukocyte count	$12,000/\mu\text{L}$	$4,500-11,000/\mu\text{L}$
Platelet count	$220,000/\mu\text{L}$	$150,000-400,000/\mu\text{L}$
Blood urea nitrogen	$14\text{ mg/dL}$	$8-20\text{ mg/dL}$
Serum creatinine	$0.8\text{ mg/dL}$	$0.7-1.3\text{ mg/dL}$

A rapid stool assay returns positive for Shiga toxin. Which of the following is the most appropriate next step in the management of this patient?

Supportive care with intravenous hydrationAnswer
B
Initiation of oral ciprofloxacin therapy
C
Administration of oral loperamide
D
Surgical consultation for exploratory laparotomy
E
Initiation of continuous venovenous hemofiltration

Answer

Supportive care with intravenous hydration

The patient's presentation of bloody diarrhea following the consumption of undercooked beef, combined with a positive Shiga toxin assay, confirms a diagnosis of Shiga toxin-producing Escherichia coli (STEC) enteritis. The cornerstone of management for STEC is supportive care, primarily focusing on fluid and electrolyte repletion. Pharmacological interventions must be carefully managed to avoid severe complications. Specifically, antibiotics are contraindicated as they can cause bacterial lysis, increasing the release of Shiga toxin into the systemic circulation and thereby escalating the risk of Hemolytic Uremic Syndrome (HUS).

Step-by-Step Solution

Analyze the patient's clinical presentation and recent exposure history.

The patient presents with acute, severe bloody diarrhea and abdominal cramping after consuming undercooked beef.

Identifying the onset, character of symptoms, and epidemiological clues is crucial for differentiating infectious from non-infectious gastrointestinal etiologies.

Interpret the diagnostic testing results.

The stool assay is positive for Shiga toxin, confirming an infection with Shiga toxin-producing E. coli (STEC).

This establishes the definitive etiology of the bloody diarrhea and guides specific management.

Evaluate laboratory results to assess for systemic complications.

Hemoglobin, platelets, blood urea nitrogen, and creatinine are all within normal limits.

STEC can precipitate Hemolytic Uremic Syndrome (HUS); however, the normal renal function and normal platelet count indicate that HUS is not currently present.

Determine the appropriate therapeutic intervention.

Select supportive care with intravenous hydration while actively avoiding antibiotics and antimotility agents.

In STEC infections, antibiotics and antimotility medications are strictly contraindicated because they increase the risk of HUS by promoting toxin release and retention, respectively.

Key Concept

The primary management of Shiga toxin-producing E. coli (STEC) gastroenteritis is strictly supportive (e.g., fluid and electrolyte replacement); antibiotics and antimotility agents are contraindicated due to the increased risk of precipitating Hemolytic Uremic Syndrome (HUS).

Question

Answer

Step-by-Step Solution

Key Concept

Common Mistakes

Topics

More questions from this topic