Acute renal failure with loin pain and patchy renal vasoconstriction

Clinical History

A physically active middle-aged woman suffering from her first episode of sudden, severe lumbosacral pain accompanied by weakness and oliguria, with normal vital signs at physical examination. She denied efforts and recent medication intake. Laboratory assays revealed increased serum creatinine (2.58 mg/dL), normal electrolytes, enzymes, urinalysis and acute phase reactants.

Imaging Findings

Initially, abdomino-pelvic sonography (not shown) excluded appreciable abnormalities, particularly involving the urinary tract. Following the early acute phase, symptoms progressively regressed spontaneously within a week and renal function improved on conservative treatment including judicious hydration.
During hospitalization, further investigation with CT (Figs.1, 2) was performed with hydration and injection of iso-osmolar contrast medium: CT confirmed both kidneys of normal size and thickness for age, and showed multiple bilateral wedge-shaped nonenhancing parenchymal regions initially interpreted as infarcts. CT-angiography images (fig.1e-g) depicted uniformly thin renal arteries compared to the usual caliber from literature [1] and to the normal appearance of other splanchnic vessels, consistent with arterial spasm.
Albeit a precipitating factor could not be identified, the self-limiting picture and characteristic CT pattern were interpreted as consistent with acute renal failure with loin pain and patchy renal vasoconstriction syndrome. Renal function normalized at discharge and follow-up ultrasound (not shown) excluded development of renal scarring.

Discussion

Initially described by Ishikawa in 1981, acute renal failure (ARF) with loin pain (LP) and patchy renal vasoconstriction (PRV) is a rare clinical syndrome which mostly occurs after anaerobic exercise without evidence of rhabdomyolysis, and is accompanied by characteristic wedge-shaped contrast enhancement on CT imaging. In 2002, a literature review identified 118 published occurrences. ARF-LP-PRV affects both sexes and is more common in physically active young males, and is differentiated from post-exercise rhabdomyolysis because myoglobinuria is absent, serum myoglobin and creatine-phosphokinase levels are normal or only mildly elevated. Approximately two-thirds of patients report history of effort (such as running) within several hours. Alternatively, analogous clinical and imaging findings have been described after heavy alcohol ingestion (17% of cases), upper respiratory infections or flu-like symptoms, medication intake (particularly analgesics and diuretics), and rarely in patients with acute lymphoblastic leukaemia and Korean haemorrhagic fever. The clinical picture is characterised by severe loin or lower back pain, accompanied by nausea or vomiting, and sometimes oliguria (in 35% of patients). Microscopic haematuria, mildly raised acute phase reactants and lactate-dehydrogenase are common. ARF-LP-PRV has a relatively good prognosis: albeit dialysis is required in 18% of patients, both symptoms and renal impairment generally last for a few days; the elevated serum creatinine (4.64±2.84 mg/dL) is generally almost normalized (average 1.40 mg/dL) at hospital discharge [2-6].

The aetiology of this uncommon syndrome remains unclear. Its pathogenesis probably involves reversible renal ischemia from temporary vasoconstriction of renal vessels, which causes both renal failure and pain. Albeit intravenous iodinated contrast is generally withheld in patients with acute renal impairment because of concern for contrast-induced nephropathy, CT is the gold standard technique for ARF-LP-PRV: the typical appearance (70% of patients) includes multiple wedge-shaped hypoenhancing regions in both kidneys, corresponding to ischemic zones due to vasoconstriction of interlobar and arcuate arteries; in this case CT-angiography documented spasm of the main renal arteries. When additional unenhanced CT scans are acquired 24-48 hours later without further contrast injection, the patchy changes show corresponding faint hyperattenuation from delayed enhancement. The key differential diagnoses are pyelonephritis and renal infarcts, the latter often characterised by preserved “cortical brim” capsular enhancement from collateral blood flow. However, in ARF-LP-PRV development of scarring is unusual and autopsy studies did not reveal renal infarction. In a few patients, kidney MRI showed “patchy” areas of T1-hyperintensity with obliterated corticomedullary contrast, and variable T2-weighted signal intensity [1, 4, 7-9].

Differential Diagnosis List

Final Diagnosis

Acure renal failure with loin pain and patchy renal vasoconstriction.

URL:	https://www.eurorad.org/case/14370
DOI:	10.1594/EURORAD/CASE.14370
ISSN:	1563-4086