A 46-year-old man comes to the emergency department due to intermittent severe right flank pain over the past few days. He has had decreased urination over the last week but has also noted occasional episodes of high urine output along with a feeling of generalized weakness. The patient has a history of chronic back pain for which he takes oxycodone daily, and he underwent a left total nephrectomy following a motor vehicle accident 25 years ago. He was recently started on low-dose lisinopril for a new diagnosis of hypertension. There is no family history of renal disease. On physical examination, blood pressure is 145/86 mm Hg and heart rate is 86/min. Laboratory results are as follows: Which of the following is the most likely cause of this patient's symptoms?

Question

A 46-year-old man comes to the emergency department due to intermittent severe right flank pain over the past few days.  He has had decreased urination over the last week but has also noted occasional episodes of high urine output along with a feeling of generalized weakness.  The patient has a history of chronic back pain for which he takes oxycodone daily, and he underwent a left total nephrectomy following a motor vehicle accident 25 years ago.  He was recently started on low-dose lisinopril for a new diagnosis of hypertension.  There is no family history of renal disease.  On physical examination, blood pressure is 145/86 mm Hg and heart rate is 86/min.  Laboratory results are as follows:  Which of the following is the most likely cause of this patient's symptoms?

Quizplus · Accepted Answer

This patient with a history of total nephrectomy now most likely has unilateral obstructive uropathy due to renal calculi. Symptoms that support this diagnosis include flank pain (renal capsular distension) and poor urine output (mechanical obstruction to urine outflow). Intermittent episodes of high-volume urination can occur when the obstruction is overcome by a large volume of retained urine (post-obstructive diuresis). Excessive diuresis may lead to potassium wasting and dehydration, both of which can cause weakness. Post-obstructive diuresis may be seen in patients with bilateral functional kidneys as the affected kidney will produce a large volume of urine when the obstruction is relieved. However, patients with a single kidney are more likely to develop acute renal failure than are those with both kidneys intact. (Choice A) Most adrenal tumors are benign and asymptomatic. Symptoms of hormone-producing adrenal tumors depend on the hormone being secreted. Nonfunctioning adrenal carcinomas may present with flank pain due to tumor growth. However, symptoms are less severe, and no change in urinary output would be expected. (Choice B) Glomerulonephritis presents with hematuria, red blood cell casts, acute renal failure, hypertension, and edema. (Choice C) The leading cause of inherited renal disease is autosomal dominant polycystic kidney disease. Patients typically present with persistent abdominal or flank pain and hematuria, which may be gross or microscopic (>3 red blood cells/hpf). There is a positive family history in 75% of cases. Over half of patients have hypertension at presentation. > (Choice D) Interstitial nephritis most frequently occurs as a drug reaction. Patients present with fever, rash, acute kidney injury, and eosinophiluria with white blood cell casts. (Choice E) Renal artery stenosis can cause hypertension with or without kidney injury. It does not cause flank pain or urinary symptoms. Educational objective: Obstructive uropathy presents with flank pain, low-volume voids with or without occasional high-volume voids, and, if bilateral, renal dysfunction.

A 46-Year-Old Man Comes to the Emergency Department Due to Intermittent