A 65-year-old woman comes to the hospital due to vague left flank pain, fatigue, and sweats for 12 days. For the past 2 days she has also had fever and nausea. The patient was treated with oral antibiotics for a urinary tract infection 4 weeks ago and has had no dysuria since, but she has lost 2.3 kg (5 lb) in the interim. Other medical conditions include type 2 diabetes mellitus and hypertension. The patient smokes a pack of cigarettes daily and uses alcohol occasionally. Temperature is 38.7 C (101.7 F), blood pressure is 130/80 mm Hg, pulse is 94/min, and respirations are 16/min. Cardiopulmonary examination is normal. Marked left flank tenderness is present. Laboratory results are as follows: Which of the following is the most likely diagnosis?

Question

A 65-year-old woman comes to the hospital due to vague left flank pain, fatigue, and sweats for 12 days.  For the past 2 days she has also had fever and nausea.  The patient was treated with oral antibiotics for a urinary tract infection 4 weeks ago and has had no dysuria since, but she has lost 2.3 kg (5 lb) in the interim.  Other medical conditions include type 2 diabetes mellitus and hypertension.  The patient smokes a pack of cigarettes daily and uses alcohol occasionally.  Temperature is 38.7 C (101.7 F), blood pressure is 130/80 mm Hg, pulse is 94/min, and respirations are 16/min.  Cardiopulmonary examination is normal.  Marked left flank tenderness is present.  Laboratory results are as follows:  Which of the following is the most likely diagnosis?

Quizplus · Accepted Answer

This patient who recently had a urinary tract infection (UTI) now has several days of unilateral flank pain, weight loss, fever, and leukocytosis, with no UTI symptoms or bacteriuria. This presentation is concerning for a renal abscess. Renal and perinephric abscesses can form in the setting of urologic infection (eg, pyelonephritis, UTI) or through hematogenous spread (eg, bacteremia, endocarditis). Necrosis of infected tissue progresses over time to cavity formation; therefore, manifestations typically develop insidiously (average ~12 days of symptoms) in patients with a history of a predisposing infection in the prior 1-2 months. Risk factors include anatomic abnormalities (eg, vesicoureteral reflux, neurogenic bladder), nephrolithiasis, uncontrolled diabetes mellitus, or tobacco use. Systemic symptoms (eg, fever, fatigue, diaphoresis, weight loss) are common. Because of the localized nature of the process, unilateral flank pain/tenderness and a palpable mass may be present, but UTI symptoms (eg, dysuria, urinary urgency) are often absent. Although urinalysis results often include pyuria, bacteriuria, and proteinuria, findings may be normal if the abscess is not in contact with the collecting ducts. Other laboratory abnormalities include leukocytosis and elevated inflammatory markers (eg, erythrocyte sedimentation rate, C-reactive protein); acute kidney injury may occur. The diagnosis is confirmed with CT scan or ultrasound. Management includes antibiotic therapy and percutaneous drainage. CT scan (Choice A) Acute interstitial nephritis can cause AKI and fever but is typically associated with rash, pyuria, and urine eosinophilia with white blood cell casts. Weight loss and flank pain would be unexpected. (Choice B) Acute papillary necrosis can cause AKI, fever, and flank pain; however, it typically causes hematuria and is most common in patients with analgesic overuse or sickle cell anemia. It does not usually cause weight loss. (Choice D) Renal cell carcinoma can cause weight loss, fever, and anemia. However, hematuria is common; and this patient's recent history of UTI with marked flank tenderness and leukocytosis is more concerning for renal abscess. (Choice E) Renal tuberculosis (due to hematogenous spread of miliary tuberculosis) can result in abscess formation or glomerulonephritis; pyuria, hematuria, urinary casts, and lower urinary tract symptoms are common. In addition, tuberculosis typically occurs in patients with risk factors (eg, incarceration, employment in high-risk health care). Educational objective: Renal and perinephric abscesses manifest with insidious onset of flank pain and systemic symptoms (eg, fever, weight loss), typically in patients with a history of urinary tract infection or extrarenal infection (eg, bacteremia) in the prior 1-2 months. In most cases, the urinalysis demonstrates pyuria, bacteriuria, and proteinuria, but it may remain normal if the abscess is not in contact with the collecting ducts.

A 65-Year-Old Woman Comes to the Hospital Due to Vague