Congenital Renal Arteriovenous Malformation Is a Rare Cause of Hematuria and Ureteric Obstruction

ABSTRACT

Renal arteriovenous malformation (rAVM) is a rare benign cause of hematuria. We present a case of a 40-year-old female with hematuria and renal colic secondary to a rAVM, as well as a review of the literature. rAVM has a female-to-male ratio of 3 to 1 and can be categorized as either congenital or acquired. Congenital rAVM constitutes 25 to 30% of all rAVM. Acquired rAVM could be categorised as iatrogenic, traumatic, inflammatory, and malignant. The diagnostic and therapeutic option of choice is renal angiography and embolisation. rAVM embolisation allows the maximal preservation of nephrons. Post-rAVM embolisation, 40 to 61% of patients are at risk of post-embolisation syndrome. Total or partial nephrectomy is reserved for recalcitrant rAVMs. Additionally, it is the treatment of choice in centers without angiography.

Yeng Kwang Tay, Dan Spernat, Patrick J Page, Caroline Dowling

Submitted: August 11, 2011 - Accepted for Publication: September 23, 2011

KEYWORDS: Renal arteriovenous malformation; Renal AVM; Hematuria; Ureteric obstruction

CORRESPONDENCE: Yeng Kwang Tay, MD, Department of Urology, Monash Medical Centre, East Bentleigh, 3165, Victoria, Australia. ()

CITATION: UroToday Int J. 2011 Dec;4(6):art 79. http://dx.doi.org/10.3834/uij. 1944-5784.2011.12.12

http://dx.doi.org/10.3834/uij.

INTRODUCTION

Renal arteriovenous malformation (rAVM) is a rare, benign cause of hematuria. Congenital rAVM has an incidence of 0.04% [1, 2]. Management options include super-selective embolization, partial nephrectomy, or radical nephrectomy. We present the case of a 40-year-old female with hematuria and renal colic, secondary to rAVM. Additionally, we provide a review of the literature.

CASE PRESENTATION

A 40-year-old fit and healthy female presented to our tertiary referral center with a 3-day history of macroscopic hematuria and renal colic. Significantly, the patient had no risk factors for an urothelial malignancy and never smoked.

Her vital signs were all within normal limits. Apart from loin-to-groin pain, the clinical examination was unremarkable. Hematology, serum biochemistry, and coagulation profiles were all normal. The contrast CT (Figure 1) showed right-sided hydroureteronephrosis to the vesicoureteric junction (VUJ). There was an ill-defined mass within the renal pelvis with a Hounsfield unit of 60. No contrast material was seen in the right collecting system or ureter in the delayed phase.

The patient was taken to theater for a cystoscopic and pyeloscopic examination. There was a significant quantity of old blood clotting in the bladder. Small fragments of clot were seen coming from the right ureteric orifice. A retrograde pyelogram demonstrated a bifid renal pelvis with a filling defect in the lower pole (Figure 2). On flexible ureteropyeloscopy, the ureter was normal. However, small fragments of clot were encountered throughout the ureter. A large organized blood clot was seen in the lower moiety pelvis, corresponding to the filling defect on the retrograde pyelogram (Figure 3). The urothelium underlying this clot appeared erythematous and vascular, raising the suspicion of rAVM. The urothelium lining the upper moiety was normal. Urine, ureteric washings, and washings from the renal pelvis were sent for cytology. Multiple biopsies of the clot were collected for histological examination. A 4.8 Fr ureteric stent was placed and bimanual examination was unremarkable.

All cytological and histological examinations revealed no evidence of malignancy. The case was reviewed at the Uro-Oncology multidisciplinary meeting and the recommendation was to perform a renal angiogram. Angiography performed by an interventional radiologist showing an AVM at the lower pole of the right kidney was clearly demonstrated with several tortuous, varix-like feeding arteries and an early filling of the renal vein. Highly selective embolization of the feeding arteries was performed. A post-coil angiography confirmed complete obliteration of the AVM. Only a small area of the lower-pole renal parenchyma was sacrificed in the procedure (Figure 4). Hematuria settled on day 1 of post-embolization. The patient required admission for pain control for 24 hours. Eight weeks post embolization, the patient was followed up by a urologist who performed a flexible cystoscopy to remove her ureteric stent. The patient reported no recurrent hematuria and flank pain. Blood tests revealed normal creatinine and estimated glomerular filtration rate. The patient was subsequently discharged to her general practitioner for renal-function surveillance and to maximize her renal health by monitoring her blood pressure, blood sugar, and lifestyle modification.

DISCUSSION

rAVM can be classified as congenital or acquired. Congenital rAVM represents 25 to 30% of all rAVM [3, 4, 5]. Formation of congenital rAVM is speculated to be due to focal abnormalities of vascular development during the first trimester of gestation [4]. The reported incidence of congenital rAVM of 0.04% is probably understated as many rAVMs do not produce any symptoms [1, 2]. It is usually asymptomatic until the third or fourth decade of life [4]. Females are 3 times more likely to be diagnosed with rAVM, with the right kidney slightly more often affected than the left [4]. Acquired rAVM constitutes 70 to 75% of all rAVM [3, 4]. Acquired rAVM can be categorized as iatrogenic, traumatic, inflammatory, and malignant (primary or metastasis) [3, 6].

Congenital rAVM is further categorized into 2 subtypes: cirsoid and aneurysmal [4]. Angiographic patterns of multiple tortuous varicosities of vascular communications formed by arterial and venous channels without interlaying capillaries, as well as early contrast filling of the draining vein, is pathognomonic for the cirsoid subtype [2, 4, 7]. The rupture of these varix-like vessels, which lie in the lamina priopria immediately beneath the urothelium, leads to hematuria [1, 2]. The aneurysmal subtype is typically defined by a solitary, cavernous channel and well-defined arterial and venous components [3, 6]. It is postulated that formation is due to an erosion of an arterial aneurysm into the venous system [3]. Patients with an aneurysmal type frequently have concomitant cardiovascular symptoms, such as hypertension [6, 8].

As rAVMs usually present with hematuria, it is vitally important to exclude malignancy of the renal parenchyma and urothelium. Standard hematuria investigations, including a urine culture, urine cytology, a 4-phase CT of the renal tract, and cystoscopy, should be performed [2, 9]. rAVM can be difficult to diagnose on ultrasound and CT. rAVM has been reported to mimic renal cysts, parapelvic cysts, and renal-cell carcinoma with IVC thrombus, as well as transitional cell carcinoma [4, 6, 10, 11]. However, a color Doppler ultrasound decreases misinterpretation of lesions compared with grey-scale ultrasound [1, 2, 9]. Naganuma reported 100% accuracy in the diagnosis of rAVM with a color Doppler US in 5 patients, later confirmed with renal angiography. The paucity of data of the CT and MRI in the diagnosis of rAVM limits their use [2]. Renal angiography is the gold standard diagnostic test for rAVM, which could be demonstrated clearly with a premature, rapid contrast enhancement of the renal vein and inferior vena cava [1, 8, 12, 13].

Angiography and embolization have replaced open surgery as the gold standard diagnostic and therapeutic option for rAVMs [4]. The advancement of technology and equipment allows a super-selective angiography and embolization of the nidus of the rAVM [4]. Research showed that, in addition to the targeted area for embolization, normal renal parenchyma infarcted in the process of super-selective renal artery embolization is in the range of 0 to 15%, allowing maximal preservation of nephrons [14, 15]. Total or partial nephrectomy is usually reserved for recalcitrant rAVMs. Additionally, it is the treatment of choice in centers without angiography.

Post-embolization syndrome (PES) occurs in 40 to 61% of patients [15]. It consists of 1 or more symptoms of fever, loin pain, nausea, and vomiting, all of which could be safely treated with analgesics and anti-emetics [15]. PES is thought to be due to tissue ischemia. However, 35 embolizations reported by Somani et al. did not support the hypothesis that PES incidence corresponds to the amount of tissue mass embolized.

CONCLUSION

Congenital rAVM is a rare cause of hematuria, especially in young patients. It is important to differentiate diagnosis as it is known to mimic various benign and malignant lesions. Renal angiography and super-selective embolization is the gold-standard tool as it is both diagnostic and therapeutic. Furthermore, it preserves the maximum number of nephrons.

REFERENCES

Brown DB, Brandes SB. Radiofrequency Ablation of a Recanalized Renal Arteriovenous Malformation. J Vasc Interv Radiol. 2005;16(3):403-406.

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