Urinary tract infection is the most common complication after kidney transplant that can cause graft loss. An early diagnosis of urinary infections decreases morbidity and mortality. Besides clinical and laboratory examinations, ultrasonography is considered as the primary imaging modality for the diagnosis of urinary tract infections. Here, we report a 53-year-old woman who presented with fever and pain at surgical site. Ultrasonography examination showed multiple, ill-defined or irregularly margined hypoechoic areas within the cortex. Ultrasonography-guided percutaneous renal biopsy was performed. Histopathologic findings were compatible with acute tubulointerstitial nephritis and multiple abscesses. Ultrasonography is the most widely applied imaging modality for diagnoses of complications after renal transplant. Although ultrasonography findings of infections are generally nonspecific, it still plays an important role in the diagnosis of urinary infections after renal transplant.

Key words : Infectious complications, Kidney transplant, Urinary infections

Introduction

Infectious complications constitute the major cause of morbidity and mortality, especially during the postoperative period in patients undergoing solid-organ transplant. The prevalence of urinary tract infections is approximately 5% to 36% and may reach up to a 60% during the first year after transplant.^1,2 Immunosuppressive medications are the major causes of infections among organ transplant reci­pients.³ Early diagnosis of urinary infections improves long-term graft survival. Ultrasonography is a relatively inexpensive and noninvasive modality that can be used to diagnose complications and to provide follow-up after transplant. Ultrasonography examination includes size and echogenicity of kidney, collecting system, and ureter, postoperative collections, and evaluation of vascular structure with color and spectral Doppler ultrasonography. Ultra­sonography may also be used for guided renal biopsy and drainage of peritransplant collections. Here, we report ultrasonography findings in a patient with acute tubulointerstitial nephritis and multiple parenchymal abscesses after renal transplant.

Case Report

A 53-year-old woman, who had undergone kidney transplant 6 months earlier, presented with fatigue, fever, leukocytosis, and pain at surgical site. Because of recurrent urinary tract infections, right nep­hrectomy operation had been performed 10 days before presentation. No recent trauma and medical interventions had been reported. Klebsiella pneu­moniae and extended-spectrum β-lactamase-producing Escherichia coli were found in the urine culture. Ultra­sonography examination showed heterogeneous parenchyma with multiple, ill-defined or irregularly margined nonvascular hypo­echoic areas within the cortex (Figure 1). No dilatation or mucosal thickening in the urine collecting system was noted. The vascular structure and flow quantification of transplanted kidney were normal in color and spectral Doppler ultraso­nography examination. No perinephric fluid collection was detected. Ultrasonography-guided percutaneous renal biopsy was performed. Histo­pathologic findings were consistent with diffuse, severe, and acute tubulo­interstitial nephritis and multiple abscesses.

Discussion

The treatment of choice for patients with end-stage renal disease is renal transplant. Urinary tract infec­tion is a common complication after kidney trans­plant, often associated with graft loss and mortality.4 Some studies have shown more urinary tract infections in female patients than in male patients. In addition, older patients have a higher prevalence of urinary tract infections than younger patients. The most common cause of urinary tract infections is bacteria. Infections caused by fungi or viruses can also been seen, but less commonly.¹

In addition to clinical and laboratory findings, imaging modalities, including ultrasonography, com­puterized tomography, and magnetic resonance, play important roles in diagnoses of urinary infec­tions after renal transplant. Ultrasonography is considered as the primary imaging technique in the evaluation of kidney transplants. Ultrasonography is nonin­vasive, inexpensive, and relatively painless and can be easily applied at bedside. The relatively low cost and safety of ultrasonography allow serial exa­minations, which may be necessary during intrao­perative or postoperative periods and for follow-up exa­minations. Ultrasonography may also be used as a guide for diagnostic and therapeutic interventions. A baseline ultrasonography evaluation is performed in the first 24 to 48 hours after transplant.⁵ The sono­graphic appearances of infections and abscesses are quite variable. Focal pyelonephritis may appear as hypoechoic or hyperechoic focal areas. These findings are nonspecific and can be misdiagnosed as infarction or rejection.^3,4 A parenchymal or perinephric abscess complicates only a minority of cases. Abscesses may be seen as fluid-filled, complicated cysts at ultraso­nography. Gas within the collection or hypoechoic focal areas in the parenchyma is highly suggestive for abscesses.^3,4 Abscesses may be treated with either ultrasonography- or computed tomography-guided percutaneous drainage.⁵

Ultrasonography is the most widely applied imaging modality for diagnosis of complications and follow-up after kidney transplant and to guide treatment. Although sonographic findings of infec­tions and abscesses are generally nonspecific or variable, ultrasonography still plays an important role in the diagnosis of urinary infections after renal transplant, due to advantages of being cost-effective and safe, having an easy application at bedside, and being available for serial examinations in intra­operative or postoperative periods.

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