Ruptured Renal Artery Aneurysm

Ruptured renal artery aneurysms can result in significant morbidity and mortality. Although renal artery aneu?rysms rarely occur, they are observed most frequently in pregnant women and are more prone to rupture in these patients. The incidence in nongravid individuals peaks in the sixth decade of life. The authors report the case of a ruptured renal artery aneurysm in a 66-year-old woman who presented with abdominal pain and coffee-ground emesis. They also review the literature and discuss the etiology, diagnosis, classification, and treatment of this pathology.

Syed Husain, MD Resident

Department of Surgery

Harlem Hospital Center

New York, NY

Sitaram Pillarisetty, MD

Assistant Clinical Professor

Department of Surgery

College of Physicians and Surgeons

Columbia University

New York, NY

Chief of Laparoscopic and Endoscopic Surgery

Department of Surgery

Harlem Hospital Center

New York, NY

Renal artery aneurysms are rarely encountered but are being diagnosed with increasing frequency due to the widespread availability of advanced imaging modalities. Most renal artery aneurysms are discovered incidentally. Rupture is rare but catastrophic, resulting in significant morbidity and mortality. Most patients with ruptured aneurysms eventually require nephrectomy. The guidelines for treating unruptured aneurysms are somewhat vague and ill-defined. We report the case of a ruptured renal artery aneurysm in a patient presenting with a massive perirenal he?matoma and discuss the management of such aneurysms.

Case report

A 66-year-old woman presented to the emergency department with a 24-hour history of abdominal pain predominantly in the right upper quadrant and epigastric region. She also reported several episodes of coffee-ground emesis associated with dizziness. Upon admission to the hospital, physical examination revealed tachycardia as well as abdominal tenderness and a vague mass in her right flank on palpation. Baseline laboratory values in?cluding urinalysis did not show any significant abnormalities. A provisional diagnosis of upper gastrointestinal (GI) bleeding secondary to peptic ulcer disease was made. An upper GI endoscopy was performed, which did not reveal any significant pathology except a bluish hue over the duodenal mucosa.

The patient subsequently developed hy?potension and was resuscitated with crystalloids and packed red blood cells. Repeated laboratory studies revealed hypovolemia and decreasing hematocrit levels. A computed tomography (CT) scan of the abdomen was performed without intravenous contrast due to the patient's increased creatinine level. Although the scan was suboptimal since contrast could not be used, it revealed a massive right perirenal hematoma (Figure). The radiology report suggested that the probable underlying pathology was a renal neoplasm or ruptured renal artery aneurysm. An emergency laparotomy was performed, which revealed a large right-sided retro?peritoneal hematoma. Further explora?tion confirmed a ruptured right renal artery aneurysm. Due to the patient's hemodynamic instability, a rapid right nephrectomy was performed and repair of the aneurysm was not attempted.

The pathology report demonstrated a 9 x 6 x 0.3-cm aneurysm with moderate atherosclerotic changes in the aneurysm wall and intramural hemorrhage. Post- o?peratively, the patient developed acute tubular necrosis that progressed to acute renal failure. She was maintained on hemodialysis for several days, and the contralateral kidney eventually regained its function.

Discussion

Epidemiology?The reported incidence of renal artery aneurysms varies greatly, ranging from 0.01% to 0.09% with a mean incidence of 0.021%.¹ These aneurysms comprise 1% of all aneurysms and 22% of all visceral aneurysms.^2,3 Renal artery aneurysms have been diagnosed with increasing frequency in recent years due to the availability of newer and more advanced imaging techniques.^1,4,5 Peak incidence occurs around 60 years of age.^4,6,7 Although most renal artery aneurysms are solitary and unilateral, as many as 30% are multiple and 20% are bilateral.^7,8

Clinical presentation?Renal artery aneurysms are usually asymptomatic. Those that produce symptoms usually have a nonspecific presentation.^4,9,10 In a review of 56 patients with renal artery aneurysms, hypertension was present in 55%, hematuria in 30%, and flank pain in 21%.⁴ A bruit may sometimes be heard over the affected side. The high rate of coincident hypertension has led to the hypothesis that renal ischemia caused by turbulence, segmental compression, or dis?tal microemboli may be the underlying etiology for raised blood pressure.^4,7,11-15

Etiology?Most renal artery aneu-r?ysms are thought to be congenital in origin, but atherosclerosis, fibromuscular dysplasia, trauma, and collagen vascular diseases have also been implicated.^7,8,15-18

Diagnosis?Most renal artery aneu-r?ysms are found incidentally on angio?grams performed for unrelated reasons.¹⁹ Contrast-enhanced CT scans are diagnostic. Angiograms provide information about the suitability of the internal iliac artery for grafting when autotransplantation is planned. As many as 60% of pa?tients with renal artery aneurysms will also have abnormal findings on an intravenous pyelogram.⁴

Classification?Renal artery aneu-r?ysms can be classified as saccular, fusiform, dissecting, or mixed.²⁰ In their review of 56 cases of renal artery aneu-r?ysms, Bulbul and Farrow described 70% as saccular, 22% as fusiform, and 5% as dissecting.⁴

Saccular aneurysms typically involve the renal artery bifurcation and are usually associated with atherosclerosis. Atherosclerosis in such cases is generally confined to the aneurysm, basically sparing the rest of the arterial tree. This finding has caused considerable debate re??garding the cause-and-effect re?lationship between atherosclerosis and aneurysm formation.²¹ Saccular aneurysms are frequently observed in children, with many occurring at bifurcations. These findings have led to the idea that the primary pathology is congenital and related to a weakness in the elastic lamina.¹⁹ Many saccular aneurysms calcify and ap?pear as ring-shaped lesions on radiography, as was observed in our patient.

Fusiform aneurysms are usually poststenotic dilatations of the renal artery. They are typically seen in patients with fibromuscular hyperplasia.

Dissecting renal aneurysms may be acute or chronic. These aneurysms are re?lated to mural fibroplasias in most cases, but they can also be iatrogenic. Acute dissecting renal aneurysms may cause renal colic, nausea, vomiting, and worsening of antecedent hypertension. Hematuria indicates severe renal ischemia. Dissecting aneurysms are true surgical emergencies warranting immediate intervention. Chronic dissections present as hypertension in most cases.^22,23

Some investigators categorize the in?trarenal aneurysm as a separate entity.⁸ These an?eurysms are commonly associated with autoimmune arteritis but may also result after trauma, as seen in patients who have undergone multiple renal biopsies.^2,21,24 False aneurysms are usually posttraumatic, as observed in patients who have undergone kidney transplantation.²⁴

Indications for treatment?Inter?vention for unruptured aneurysms should be undertaken in patients presenting with renovascular hypertension, progressive enlargement of the aneurysm, symptomatic aneurysms (hematuria or flank pain), large aneurysms (> 3 cm), and those who could be pregnant. Some surgeons suggest that patients with limited renal reserve should also undergo elective surgery because rupture may necessitate nephrectomy.^7,12 The incidence of rupture during pregnancy has been re?ported to be as high as 80%, making surgery an absolute indication for pregnant patients and for those who intend to get pregnant.^4,11 Some authors suggest that lack of calcification in the aneurysm wall and enlargement of the aneurysm should also be considered indications for surgery.⁸ Although elective repair of asymptomatic renal artery aneurysms generates much debate, most authorities agree that aneurysms larger than 3 cm in diameter should be repaired in patients without significant comorbidities.^{1-5,7,8,21,22,24}

Managing these aneurysms may result in abatement or improved control of hypertension.⁴ Selective renal venous sampling for renin is required to identify patients who will benefit from surgery. If adequate diagnostic support is lacking, surgery on these aneurysms to control hypertension may lead to disappointing results even after a technically successful repair.²³

Aneurysm rupture?Renal artery an?eurysms rarely rupture, particularly when the aneurysm is small. An analysis of 36,656 autopsies did not show one case of ruptured renal artery aneurysm.⁶ Tham and colleagues followed 69 pa?tients with renal artery aneurysms that were treated conservatively over a mean of 4.3 years without any evidence of rupture.⁶ In a similar series, Hubert and associates also did not encounter any cases of rupture.¹⁶ In a review by Schorn and colleagues, 207 patients with renal artery aneurysms were observed for a mean period of 5.3 years.¹ No ruptures were encountered during this period. The incidence of rupture appears somewhat higher in cases of noncalcified and in?trarenal aneurysms.^11,18

Pregnant women make up a disproportionate percentage of the patients with ruptured renal artery aneurysms. Rupture in nonpregnant individuals is exceedingly rare.¹⁵ In 1997, a literature review by Schorn and colleagues found 39 cases of ruptured aneurysms, 23 of which occurred in pregnant women.¹ Rupture in a pregnant patient is associated with high fetal and maternal mortality rates.^1,5,7 A combination of hormonal influences and altered hemodynamics during pregnancy may be partly responsible for the high rate of rupture in these patients.¹ Several factors have been im?plicated as the final pathway leading to arterial wall weakness during pregnancy. These include hyperplasia of arterial intima and media combined with a loss of mucopolysaccharides and fragmentation of reticulum fibers.^7,18

Management?Early diagnosis and rapid intervention are imperative for successful management. Similar to their unruptured counterparts, ruptured renal artery aneurysms present with nonspecific symptoms, making diagnosis difficult. Once ruptured, it is seldom possible to salvage the involved kidney due to extensive retroperitoneal hematoma and hemodynamic instability.^1,15,18 This is par?ticularly true if rupture involves the right side because dissection on this side is more complex and technically de?manding. Left-sided ruptures are more amenable to reconstruction.¹⁵ Every ef?fort should be made to ensure that the patient has a functional contralateral kidney before proceeding with a nephrectomy. Treatment options include en?do?vascular embolization in high-risk pa?tients who are poor surgical candidates. Tan?gential aneurysmectomy and primary aneurysmorrhaphy may be attempted for smaller aneurysms, but most will require a vascular autograft. The procedure can be performed in situ or carried out ex vivo with renal autoimplantation. Aortorenal bypass may be the procedure of choice in cases where the proximal portion of the renal artery is involved. Partial or total nephrectomy may be necessary for intrarenal aneurysms. Gill and colleagues described the first case of laparoscopic renal artery aneurysm re?pair.²⁵ With recent advancements in la?p?aroscopic surgery, this may be a viable treatment option in the future.

Conclusion

Ruptured renal artery aneurysms are rare but catastrophic. Although recent advances in imaging have facilitated diagnosis, guidelines for treatment and optimal time for intervention are still heavily debated. Early diagnosis and prompt intervention are the cornerstones of management and patient survival. l l

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