Emergency medical services bring an 81-year-old male to the emergency department due to th… — USMLE Step 3

Emergency medical services bring an $81$ -year-old male to the emergency department due to the abrupt onset of right-sided lower abdominal pain and an inability to bear weight on his right leg. The symptoms started $3$ hours ago while he was resting in his chair at an assisted living facility. His medical history is significant for permanent atrial fibrillation, essential hypertension, and benign prostatic hyperplasia. His current medications include rivaroxaban, lisinopril, and tamsulosin.

On presentation, his blood pressure is $88/54\text{ mmHg}$ , and his pulse is $118/\text{min}$ and irregularly irregular. He appears pale, diaphoretic, and anxious. Abdominal examination reveals a soft, non-distended abdomen with localized tenderness in the right lower quadrant. There is no rebound tenderness, guarding, or pulsatile mass. Bowel sounds are normoactive. Neurological examination of the right lower extremity reveals $3/5$ strength in hip flexion and decreased pinprick sensation over the anterior thigh. Strength and sensation are fully intact in the left lower extremity. Distal pulses are $2+$ and symmetric bilaterally.

Laboratory studies show:
Hemoglobin: $7.8\text{ g/dL}$ (baseline $12.1\text{ g/dL}$ one month ago)
Leukocyte count: $8,400/\text{mm}^3$
Platelet count: $180,000/\text{mm}^3$
Serum creatinine: $1.1\text{ mg/dL}$

Which of the following is the most likely diagnosis?

Iliopsoas hematomaAnswer
B
Ruptured abdominal aortic aneurysm
C
Acute aortoiliac occlusion
D
Iliopsoas abscess
E
Deep vein thrombosis of the external iliac vein

Answer

Iliopsoas hematoma

Iliopsoas hematoma is the most likely diagnosis. The patient is on a direct oral anticoagulant (rivaroxaban) and presents with acute hemorrhagic shock, evidenced by hypotension, tachycardia, and a precipitous drop in hemoglobin. The bleeding is localized to the retroperitoneal space within the psoas muscle. This anatomical location explains both the right lower quadrant pain and the classic signs of femoral nerve compression, which include weakness in hip flexion (iliacus and psoas muscles) and decreased pinprick sensation over the anterior thigh.

Step-by-Step Solution

Analyze the patient's hemodynamic status and laboratory findings.

The patient exhibits hypotension, tachycardia, and a severe acute drop in hemoglobin (

12.1

down to

7.8\text{ g/dL}

), indicating acute hemorrhagic shock.

Identifying the primary physiological derangement (hemorrhage) narrows the differential diagnosis to bleeding sources, especially given his use of rivaroxaban.

Correlate the physical examination findings to localize the source of the hemorrhage.

The patient has right lower quadrant abdominal pain coupled with specific right-sided neurological deficits: weakness in hip flexion and decreased sensation over the anterior thigh.

These specific neurological findings perfectly map to a femoral nerve palsy, suggesting a space-occupying lesion compressing the nerve as it travels.

Synthesize the anatomic localization with the clinical syndrome to formulate the diagnosis.

A bleeding event in the retroperitoneal space involving the psoas muscle (iliopsoas hematoma) explains the acute blood loss, the abdominal pain, and the direct compression of the femoral nerve.

Combining the risk factor (anticoagulation), the systemic sign (hemorrhagic shock), and the localizing sign (femoral neuropathy) confirms the diagnosis of iliopsoas hematoma.

Key Concept

Formulating a differential diagnosis for acute abdominal pain with hemorrhagic shock and localized neurological deficits in an anticoagulated patient.

Question

Answer

Step-by-Step Solution

Key Concept

Common Mistakes

Topics

More questions from this topic