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Apr 13

Recurrent Episodes of Acute Kidney Injury in a Kidney Transplant Recipient

A 59-year-old man who had undergone orthotopic heart transplantation developed calcineurin inhibitor nephrotoxicity, which led to a deceased donor kidney transplantation. Five years later, he presented with an increase in serum creatinine level from 1.1 mg/dL (corresponding to an estimated glomerular filtration rate [eGFR] of 71 mL/ min/1.73 m2 calculated by the CKD-EPI [Chronic Kidney Disease Epidemiology Collaboration] equation) to 3.2 mg/dL (eGFR, 19 mL/min/1.73 m2). He had no urinary symptoms, but reported discomfort in the abdomen and back after working on his boat. On physical examination, his kidney transplant was not readily palpable, but a bruit was audible. Urinalysis showed proteinuria (3+) and hematuria (4+), as well as 3-5 granular casts, 2-3 white blood cells, and occasional tubular epithelial cells per high-power field. Kidney biopsy and ultrasonography were performed. Spontaneously, urine output increased with a marked improvement in serum creatinine level to 1.2 mg/dL (eGFR, 64 mL/min/1.73 m2), and he was discharged. He was readmitted a month later with abdominal pain, vomiting, diarrhea, fevers, chills, and acute kidney injury (AKI). Results of computed tomography (CT) of the abdomen and pelvis were consistent with transplant pyelonephritis. He was treated with intravenous fluids and antibiotics, although his urine culture remained negative. He was initially oliguric and his serum creatinine level peaked at 9 mg/dL (eGFR, 6 mL/min/1.73 m2), but then improved upon resolution of his abdominal symptoms. Comparing the initial CT scan to a CT angiogram that was obtained 3 months later yielded the diagnosis.

DISCUSSION

1. What are the causes of late-onset decreased transplant function?

Causes of late-onset decreased transplant function (in which “late” is > 6 months after transplantation) can be grouped into prerenal, vascular, immunologic, infectious, and other intrinsic renal and urologic causes. Traditional causes of AKI, such as acute tubular necrosis, decreased kidney perfusion, and obstruction, remain important causes of late-onset decreased transplant function. Vascular causes include renal artery stenosis and thrombotic microangiopathy. Urologic causes include ureteric strictures, nephrolithiasis, and bladder outlet obstruction. Immunologic causes include late acute rejection and chronic transplant glomerulopathy. Common infectious causes of late-onset decreased transplant function include polyoma (BK) virus nephropathy and urinary tract infections. Intrinsic renal causes include calcineurin inhibitor nephrotoxicity and recurrent or de novo glomerular disease.

2. What were the biopsy and radiographic findings?

The biopsy specimen showed ischemic wrinkling of glomerular basement membranes, mild chronic interstitial fibrosis, and mild tubular atrophy. There was no evidence of tubulitis or tubular injury that would suggest interstitial nephritis, cellular rejection, or tubular necrosis. The spectral color Doppler ultrasound showed parvus tardus waveforms in the superior and inferior intrarenal arteries. Ultrasound findings were concerning for renal artery stenosis, but this diagnosis did not readily explain the spontaneous improvement in symptoms and kidney function.

3. What is the diagnosis?

The patient has experienced torsion of the transplant kidney around its vascular pedicle. The CT angiogram shows the transplant kidney in the left pelvis, but in a different orientation than was observed in the CT performed during the second admission with AKI. The ultrasound findings of parvus tardus waveforms can be explained by kinking of the renal artery after the kidney had moved further into the pelvic cavity and away from the left external iliac vessels. It rotated 90� on its long axis to be oriented cephalad to caudad. This is an under-recognized vascular cause of late-onset decreased transplant function that to our knowledge has been described in only intraperitoneally placed transplanted kidneys. Review of the patient’s surgical procedure showed that the kidney had been anastomosed to the left external iliac artery and then placed in an intraperitoneal position due to poor positioning when placed extraperitoneally.

4. What is the treatment of this condition?

Complete torsion warrants emergent surgical exploration and detorsion to salvage the kidney from total infarction. Episodic partial torsion with spontaneous detorsion (as in our case) should be managed by fixing the transplant to the anterior abdominal wall (nephropexy), which eliminates the risk of recurrence of torsion of the kidney transplant.

FINAL DIAGNOSIS

Recurrent torsion of a transplanted kidney resulting in AKI.

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