A 54-year-old man comes to the hospital due to acute-onset right flank pain associated with nausea. Five years ago, the patient had nephrolithiasis; the renal calculi passed spontaneously with intravenous fluids. Review of systems is positive for occasional palpitations. Other medical problems include hypertension, obesity, and obstructive sleep apnea. Temperature is 38 C (100.4 F), blood pressure is 170/98 mm Hg, pulse is 90/min, and respirations are 18/min. Cardiopulmonary examination shows no abnormalities. Right flank tenderness is present. Urinalysis demonstrates 2+ red blood cells and no white blood cells or protein. A representative kidney specimen is shown below: Which of the following is the most likely diagnosis?

Question

A 54-year-old man comes to the hospital due to acute-onset right flank pain associated with nausea.  Five years ago, the patient had nephrolithiasis; the renal calculi passed spontaneously with intravenous fluids.  Review of systems is positive for occasional palpitations.  Other medical problems include hypertension, obesity, and obstructive sleep apnea.  Temperature is 38 C (100.4 F), blood pressure is 170/98 mm Hg, pulse is 90/min, and respirations are 18/min.  Cardiopulmonary examination shows no abnormalities.  Right flank tenderness is present.  Urinalysis demonstrates 2+ red blood cells and no white blood cells or protein.  A representative kidney specimen is shown below:  Which of the following is the most likely diagnosis?

Quizplus · Accepted Answer

11ec160b_3a4f_003a_9249_1fc0e8921df3_MD0001_00 This patient with flank pain, low-grade fever, and hematuria has a renal infarction. Renal infarctions are most commonly caused by cardioembolic disease (ie, originating from the left atrium or ventricle). Atrial fibrillation, suggested by this patient's intermittent palpitations and history of sleep apnea, is the greatest risk factor, although emboli from mural thrombi (following myocardial infarction), prosthetic valves, or valvular vegetations (ie, endocarditis) are also implicated. Complete occlusion of the renal artery can occur more rarely due to direct arterial injury (eg, dissection, vasculitis) or hypercoagulable states (eg, antiphospholipid syndrome). The kidneys are predisposed to embolic infarctions due to their high perfusion rates and limited collateral circulation. Typical presenting symptoms include flank pain, nausea, vomiting, and low-grade fever. Hypertension can occur due to renin release from hypoxic renal tissue. Common laboratory abnormalities include elevated lactate dehydrogenase (suggesting cell necrosis), hematuria, and mild leukocytosis; however, serum creatinine is often normal unless bilateral or massive unilateral disease is present. Gross pathology shows sharply demarcated, yellow-white, wedge-shaped infarcts surrounded by hyperemic tissue. (Choice A) Nephrolithiasis can cause flank pain and hematuria, but renal injury is typically due to obstruction, causing hydronephrosis. Renal calyces and ureters are dilated, and infarctions do not occur. (Choice B) Pyelonephritis can also cause flank pain and nausea, and focal abscesses are usually present. However, pyuria is expected on urinalysis and patients typically have dysuria. (Choice C) Renal cell carcinoma can cause flank pain and hematuria, but gross pathology demonstrates yellow, well-circumscribed lesions with areas of focal hemorrhage. (Choice E) Papillary necrosis, often caused by excessive chronic analgesic use, demonstrates cortical atrophy with necrotic, sloughing papillae. Focal, wedge-shaped necrosis is not seen. Educational objective: Renal infarctions are most commonly caused by cardioembolic disease; atrial fibrillation is the greatest risk factor. Clinical features include flank pain, nausea, vomiting, low-grade fever, and hypertension (due to renin release from hypoxic tissue). Gross pathology demonstrates sharply demarcated, yellow-white, wedge-shaped areas with surrounding hyperemia.

A 54-Year-Old Man Comes to the Hospital Due to Acute-Onset