Case Presentation: A 37 year-old female with history of menorrhagia on oral contraceptives (OCP) for 2 months, presented with abrupt onset of right lower quadrant abdominal pain (RLQ) for 1 day. Pain was 10/10, constant, sharp, with radiation to right flank, without alleviating factors. Pain was associated with nausea and multiple episodes of vomiting. She denied dysuria, frequency, hematuria, or vaginal discharge. Upon admission, she was afebrile, but appeared in distress secondary to pain. She had tenderness to palpation over RLQ, right groin, flank, and the lower back. Labs notable for: WBC 12.3 K/uL, Cr 1.23 mg/dL, AST 81 U/L, ALT 58 U/L, LDH 2124 U/L. Urinalysis was negative for infection and hematuria but Ceftriaxone was started due to concerns for Pyelonephritis. CT abdomen and pelvis revealed a right kidney with multiple wedge-shaped regional areas of low enhancement extending to the cortex, suggestive of infarct. There was no significant perinephric stranding. CT angiogram of the abdomen showed persistent abnormality in the enhancement pattern. The right renal artery appeared normal proximally, but more conspicuous in the branches supplying the spared upper and lower poles. As concern for renal artery thrombosis arouse, hypercoagulable workup was pursued, which revealed abnormal Antithrombin III activity. Antibiotics were stopped and anticoagulation with Heparin drip was initiated. She was eventually discharged on Lovenox 1mg/kg BID for a 6 month period, with plan to follow up with Hematology team. The OCP were discontinued as well.

Discussion: Abdominal pain with radiation to the flank can be suggestive of pyelonephritis but other differential diagnoses should be entertained, especially if the patient’s condition is not improving after initiation of treatment with antibiotics. While pyelonephritis is common, acute renal artery infarction (RAI) is a rare condition, with similar manifestations. Furthermore, in 6% of radiographic imaging consistent with acute pyelonephritis, an underlying infarct has been the culprit, due to underlying thrombophilia, thus proprogating additional hypercoagulable work-up.
Renal artery infarction should be suspected when presented with the following triad: persistent abdominal and/or flank pain, elevated serum LDH and/or hematuria, and risk of thromboembolic event. LDH concentration, a marker of cell necrosis, is high in up to 90.5% of the total population with RAI. Once RAI is suspected, contrast-enhanced CT should be pursued as this initial diagnostic modality can identify 80% of cases. CT scan will reveal wedge-shaped, peripheral non enhancing areas, with presence of cortical rim sign in some cases.

Our patient presented with the triad of RAI previously described and on imaging evaluation, was found with the classical wedge-shaped, peripheral non-enhancing areas consistent with this diagnosis. The absence of infection in the urinalysis, and lack of significant perinephric stranding on the CT A/P argued against pyelonephritis in our case. Antibiotics were appropriately discontinued and she was started on anticoagulation as indicated.

Conclusions: Renal artery infarction is a rare phenomenon with a nonspecific presentation that can mimic more common conditions such as pyelonephritis. Elevated LDH levels is suggestive of RAI and may help differentiate between this and other etiologies. Due to the risk of irreversible damage to the kidneys from delayed recognition, prompt confirmation with CT imaging and treatment with anticoagulation is paramount.