A female patient, aged 68, presents to the acute care clinic accompanied by her family. Sh… — USMLE Step 2 CK

A female patient, aged $68$ , presents to the acute care clinic accompanied by her family. She reports progressive abdominal swelling, nausea, vomiting, and exertional shortness of breath over the past $14$ days. Her medical history is notable for asthma, primary hypothyroidism, and Hodgkin lymphoma that was treated with mantle field radiation therapy $25$ years ago. Her home medications include levothyroxine and as-needed albuterol.

Her temperature is $37.1^\circ\text{C}$ ( $98.8^\circ\text{F}$ ), blood pressure is $98/60\text{ mmHg}$ , pulse is $108\text{/min}$ , and respirations are $24\text{/min}$ . Pulse oximetry is $94\%$ on room air.

Physical examination reveals a chronically ill-appearing woman. The jugular veins are distended to $14\text{ cm } H_2O$ , and the distension increases with inspiration. Chest auscultation reveals diminished breath sounds at the bases bilaterally, with no wheezes or crackles. Cardiac examination shows a rapid, regular rhythm with a sharp, early diastolic sound heard best at the left sternal border. The abdomen is markedly distended and tympanitic, with sluggish bowel sounds and shifting dullness. There is $3+$ pitting edema of the lower extremities bilaterally.

Laboratory studies are as follows:

Laboratory Test	Result	Reference Range
Sodium	$132 \text{ mEq/L}$	$136-145 \text{ mEq/L}$
Potassium	$4.8 \text{ mEq/L}$	$3.5-5.0 \text{ mEq/L}$
Chloride	$98 \text{ mEq/L}$	$98-106 \text{ mEq/L}$
Bicarbonate	$14 \text{ mEq/L}$	$22-28 \text{ mEq/L}$
Blood urea nitrogen	$42 \text{ mg/dL}$	$8-20 \text{ mg/dL}$
Creatinine	$1.6 \text{ mg/dL}$	$0.6-1.2 \text{ mg/dL}$
TSH	$0.1 \text{ } \mu\text{U/mL}$	$0.4-4.0 \text{ } \mu\text{U/mL}$
Free T4	$0.6 \text{ ng/dL}$	$0.9-1.7 \text{ ng/dL}$

Arterial Blood Gas (Room Air)	Result	Reference Range
pH	$7.30$	$7.35-7.45$
PaCO2	$29 \text{ mmHg}$	$35-45 \text{ mmHg}$
PaO2	$72 \text{ mmHg}$	$75-105 \text{ mmHg}$

An upright abdominal radiograph shows multiple dilated loops of small bowel with air-fluid levels. Electrocardiography reveals sinus tachycardia with low-voltage QRS complexes.

Which of the following is the most appropriate next step in the management of this patient?

Transthoracic echocardiographyAnswer
B
Surgical consultation for exploratory laparotomy
C
Intravenous administration of $NaHCO_3$
D
Increase the daily dosage of levothyroxine
E
Administration of nebulized albuterol and intravenous methylprednisolone

Answer

Transthoracic echocardiography

The correct answer is transthoracic echocardiography. This patient's presentation of progressive right-sided heart failure (elevated jugular venous pressure, Kussmaul sign, peripheral edema, ascites), along with an early diastolic sound (pericardial knock), is classic for constrictive pericarditis. Her history of mantle field radiation for Hodgkin lymphoma

25

years ago strongly predisposes her to this condition. The severe right heart failure leads to marked systemic venous congestion, causing congestive hepatopathy, ascites, and bowel wall edema (congestive enteropathy). This manifests clinically and radiographically as an adynamic ileus, with dilated bowel loops and air-fluid levels mimicking a mechanical obstruction. Transthoracic echocardiography is the most appropriate next step to assess for signs of constrictive pericarditis, such as increased pericardial thickness, abnormal septal motion (septal bounce), and respiratory variation in ventricular filling.

Step-by-Step Solution

Identify the primary cardiovascular pathology based on physical exam and medical history.

The patient has signs of severe right-sided heart failure (elevated jugular venous pressure, Kussmaul sign, peripheral edema, ascites) and a pericardial knock, strongly suggesting constrictive pericarditis.

Mantle radiation is a classic risk factor for late-onset constrictive pericarditis. The clinical findings are highly specific for restricted ventricular filling.

Evaluate the prominent gastrointestinal symptoms and radiographic findings in the context of the primary diagnosis.

The nausea, vomiting, abdominal distension, and dilated bowel loops represent an adynamic ileus (congestive enteropathy).

Severe right heart failure transmits elevated pressures backward, causing profound splanchnic venous congestion and bowel wall edema, which clinically mimics a mechanical small bowel obstruction.

Analyze the acid-base and endocrine laboratory abnormalities.

Winter's formula (

PaCO_2 = 1.5 \times 14 + 8 \pm 2 = 29 \pm 2

) confirms an appropriately compensated metabolic acidosis. The concurrent low TSH and low free T4 indicate euthyroid sick syndrome.

Both abnormalities are expected physiological responses to poor tissue perfusion and critical illness, ruling out a mixed acid-base disorder or undertreated primary hypothyroidism.

Determine the most appropriate next step in management.

Transthoracic echocardiography should be performed immediately.

Echocardiography will confirm the diagnosis of constrictive pericarditis by demonstrating pericardial thickening, a septal bounce, and respiratory variation in ventricular inflow.

Key Concept

Severe right-sided heart failure (e.g., from radiation-induced constrictive pericarditis) can cause profound systemic venous congestion leading to congestive hepatopathy and enteropathy, which may present as an adynamic ileus mimicking a surgical abdomen. Recognition of classic signs like Kussmaul sign and a pericardial knock is vital to identify the cardiac etiology.

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