RENAL VEIN THROMBOSIS IN ACUTE PYELONEPHRITIS - RARE OR RARELY DIAGNOSED ?

Introduction:

Renal vein thrombosis (RVT) is a rare but potentially life-threatening complication of acute pyelonephritis (APN). APN and RVT share overlapping clinical features, making accurate diagnosis challenging. We present two cases emphasizing the underdiagnosis of RVT in APN. The cases underscore that RVT in APN is likely more common than reported in the literature. Early recognition and prompt management are crucial to prevent severe complications such as pulmonary embolism. Further research is needed to explore the underlying mechanisms and risk factors, highlighting the importance of increased awareness among clinicians.

Methods:

Case 1: A 52-year-old female with poorly controlled diabetes mellitus presented with fever, chills, vomiting, and left flank pain for five days. She was febrile with stable vitals. Laboratory investigations revealed leukocytosis, normal renal functionand hypoalbuminemia (serum albumin of 2.7 g/dL). Urinalysis showed pyuria and microscopic haematuria with no significant proteinuria. Urine culture grew E. coli. Ultrasound revealed a bulky left kidney with mild hydronephrosis. CT urogram showed a 38×41 mm anterior left renal cortical abscess extending into the perinephric space. Imaging with contrast-enhanced CT scan demonstrated multiple left renal abscesses with perinephric collections and a non-occluding thrombus in the left renal vein (Figure 1). APLA, procoagulant and autoimmune workup were negative. The patient was managed with broad-spectrum IV antibiotics, insulin, and other supportive treatments. Left retrograde pyelography and DJ stenting were performed. She was discharged with oral anticoagulant (Apixaban 5mg twice daily) and IV antibiotics (Meropenem) was continued for a total of 14 days.  

Case 2: A 53-year-old female with no prior comorbidities presented with high-grade fever and left loin pain. Laboratory investigations revealed leukocytosis, normal renal function and mild transaminitis. Urinalysis showed pyuria and microscopic haematuria but no proteinuria. Urine culture grew E. coli. Ultrasound revealed mild left-sided perinephric fluid. CT urogram showed mild enhancing wall thickening of the left renal pelvis and upper ureter, complete occlusion of the left renal vein involving IVC, and partial thrombosis of the adjacent left lumbar vein (Figure 2). Procoagulant and other thrombophilic workup was negative. She was managed with IV antibiotics (Meropenem), low molecular weight heparin, and other supportive therapy and continued on oral anticoagulant (Apixaban 5mg twice daily). 

Results:

Diagnosing RVT is challenging due to its nonspecific symptoms and the need for contrast imaging modalities. Colour Doppler can detect flow, but has poor sensitivity and is operator dependant. CT angiography is currently the imaging modality of choice, with nearly 100% sensitivity and specificity. Magnetic Resonance Angiography (MRA) is an alternative, offering high contrast images , avoids radiation and nephrotoxic contrast agents, albeit at a higher cost. Early anticoagulation is crucial to prevent thrombus propagation and serious thromboembolism. Initial anticoagulation is typically achieved with parenteral heparin, followed by long-term oral anticoagulant therapy. The duration of anticoagulation varies, often depending on the recurrence of RVT or the presence of risk factors. Thrombolytics are generally reserved for patients with severe disease, poor prognosis, massive clot burden, and bilateral RVT with acute renal failure.RVT secondary to acute pyelonephritis is rare and only few cases are described in the literature till date. We used data published in previous case reports to manage the above two cases and both are asymptomatic at 3 months follow-up. The characteristics of the previous case reports (we did not include case reports with limited data) including our two cases is summarised in the table below (Table 1). 

Both our cases were females and had gram negative bacteremia which was similar to most of the earlier reported cases. One very striking observation within the earlier case reports is good recovery with complete resolution of RVT in all the reported cases of APN, as compared to RVT in nephrotic syndrome, having a reported mortality of 40% by Laville et al. However, we do not have data to compare the long term outcome of all the reported cases of RVT in APN. Diabetes, gram negative bacteremia and post menopausal state in these patients may contribute to the increased risk of renal vein thrombosis in patients with APN. 

Diagnosing RVT is challenging due to its nonspecific symptoms and the need for contrast imaging modalities. Colour Doppler can detect flow, but has poor sensitivity and is operator dependant. CT angiography is currently the imaging modality of choice, with nearly 100% sensitivity and specificity. Magnetic Resonance Angiography (MRA) is an alternative, offering high contrast images , avoids radiation and nephrotoxic contrast agents, albeit at a higher cost. Early anticoagulation is crucial to prevent thrombus propagation and serious thromboembolism. Initial anticoagulation is typically achieved with parenteral heparin, followed by long-term oral anticoagulant therapy. The duration of anticoagulation varies, often depending on the recurrence of RVT or the presence of risk factors. Thrombolytics are generally reserved for patients with severe disease, poor prognosis, massive clot burden, and bilateral RVT with acute renal failure.

Conclusions:

The possibility of an undiagnosed non-occlusive renal vein thrombosis cannot be ruled out in patients with APN especially in the setting of poorly controlled Diabetes. Early diagnosis and prompt management can have good outcomes and is the key to prevent severe complications. A subset of patients who succumb to APN may be harbouring an undiagnosed RVT, as renal dysfunction and poor breath holding make the diagnostic modalities of contrast CT and renal doppler difficult. Hence, to throw the light on whether RVT in APN is actually rare or it is rarely diagnosed, more data is needed. 

I have no potential conflict of interest to disclose.

I did not use generative AI and AI-assisted technologies in the writing process.