Kidney and Ureter Vascular Disorders

Kidney and Ureter Vascular Disorders

Abdullah Zreik1 and Omar M. Aboumarzouk1, 2

1 Glasgow Urological Research Unit, Department of Urology, Queen Elizabeth University Hospital, Glasgow, UK

2 University of Glasgow, School of Medicine, Dentistry & Nursing, Glasgow, UK


Variations of the renal vessels are not uncommon. These vascular abnormalities are usually diagnosed using computed tomography (CT) or angiography. Knowledge of the normal anatomy of the renal vessels and the various abnormalities is important for every surgeon who operates on the kidneys to avoid inadvertent injury.

Keywords: renal artery; renal vein; stenosis; aneurysm; haemangioma

15.1 Congenital Anomalies of the Renal Vessels

The pattern of the arterial supply of the kidney was established by Graves in 1971 [1]. There are five main renal segments arranged like the fingers of the hand (Figure 15.1). There are many variations: two or three of the main branches may spring from a common trunk or arise separately from the aorta (multiple renal arteries) [1]. Aberrant arteries usually originate form vessels other than the aorta and the main renal artery. They could arise from the lumbar, gonadal, common, and external iliac arteries [2]. The term ‘accessory artery’ is used when two arteries supply the same renal segment. These variations are more common in pelvic kidney or renal ectopia. It is common for the upper segmental vessel to cause an indentation on the neck of the upper calix, an appearance which can be mistaken for a tumour (Figure 15.2). Very rarely this artery can cause actual obstruction [3]. The relationship between the artery and the vein could vary (i.e. artery dorsal to the vein, artery ventral to the vein, or artery cranial and caudal to the vein).

Illustration depicting the arrangement of renal artery branches connected to the kidneys.

Figure 15.1 Underlying arrangement of renal artery branches: four anterior and one posterior.

Image described by caption.

Figure 15.2 Urogram showing upper calix indented by upper pole segmental artery.

Aberrant, accessory, or multiple vessels may constrict the pelviureteric junction causing symptoms like haematuria, pain, urinary tract infections, and calculi.

The anatomy could be confirmed using arteriography or contrast computed tomography (CT).

15.1.1 Haemangioma

It is unclear whether these should be considered to be benign hamartomas or congenital anomalies of the renal arteries. They occur in all sizes, from minute capillary naevi on a papilla to large arteriovenous malformations.

The main symptom is repeated or persistent haematuria, sometimes accompanied by clot colic. Only with large malformations are there any physical signs; then, there may be hypertension and a bruit heard over the loin.

The routine investigations for haematuria, cystoscopy and retrograde urogram reveal blood issuing from one ureter. CT or an angiogram will confirm the diagnosis, but in small angiomas, there is no mass and nothing shows up on the CT scan. Even an angiogram may fail to detect the source of the bleeding in some cases.

Ureteropyeloscopy may show blood issuing out of one of the calices and allow it to be coagulated using laser (Figure 15.3). Otherwise a partial nephrectomy may be possible [4].

Diagram depicting percutaneous nephroscopy (left) and ureteroscopy (right). Left: A flexible nephroscope inserted into the kidney. Right: A flexible ureteroscope inserted into the ureter.

Figure 15.3 Ureteroscopy or percutaneous nephroscopy may reveal a tiny aneurysm in a calix and allow it to be laser coagulated.

15.1.2 Renal Segmental Hypoplasia (Ask–Upmark Kidney)

This is a rare deformity of the kidney seen in younger patients with hypertension [5]. Histologically, it is characterised by absence of glomeruli and the thickening of arterial wall which appears stenosed [6]. The kidney is grossly scarred and has similar appearances to reflux nephropathy without the inflammatory changes [7].

Most patients present with hypertension at a young age. Recurrent urinary tract infections (UTIs) are a rare manifestation.

The renal function could be normal as the condition could be unilateral. Renal ultrasound or CT will reveal an atrophic scarred kidney. Mercaptotriglycerine (99Tc‐Mag3) or dimercaptosuccinic acid (DMSA) renogram can confirm the reduced renal function; arteriography will show a small renal artery.

15.2 Renal Artery Disorders

15.2.1 Traumatic Lesions of the Renal Artery

Blunt renal injuries are rare (i.e. overall incidence 0.05% of all blunt injuries) [8]. It is associated with deceleration injuries (e.g. road traffic accidents and falls from heights) [8]. Injuries to the ribs or other abdominal organs such the spleen, liver, or bowels are usually present. The injury can vary between a small leak, thrombosis, or complete avulsion and is best diagnosed with CT or angiogram. Conservative management is the most common treatment; however, surgical exploration with revascularisation or nephrectomy could be performed in patients who are unstable. Revascularisation is difficult and associated with reduced renal function [9]. This is usually reserved for patients with traumatic thrombosis who have a single kidney or bilateral injuries [9, 10].

Penetrating injuries of the renal artery are a common cause of arteriovenous fistula in incidents involving knives. Elsewhere, the most common cause is iatrogenic during renal biopsy or partial nephrectomy. There is more than the usual retroperitoneal haematoma, and within a few weeks, the patient develops a thrill and bruit over the loin, sometimes with haematuria [11]. The diagnosis is confirmed with CT or arteriography (Figure 15.4). Small lesions may be embolised through an angiographic catheter [11]. Larger ones may require partial nephrectomy. Very large arteriovenous fistulae with a large shunt and loss of renal parenchyma require nephrectomy.

Diagram displaying an angiographic catheter inserted into the blood vessel then to the artery (connected to the kidney) with plug of gelform.

Figure 15.4 A small traumatic arteriovenous aneurysm may be embolised at angiography.

15.2.2 Renal Artery Stenosis

Atherosclerosis is the most common cause of renal artery lesions [12]. Plaques of atheroma may affect the main renal artery at the junction with the aorta or along its major branches (Figure 15.5). A different pathological process affects medium‐sized vessels such as the arcuate arteries where the internal elastic lamina is doubled and redoubled – intimal fibroelastic hyperplasia (Figure 15.6). A third change – arteriolosclerosis – where hyaline material accumulates just under the intima, is seen in the small afferent arterioles of the glomeruli (Figure 15.5).

Diagram of a kidney with intimal fibroelastic hyperplasia and arteriolosclerosis.

Figure 15.5 Atheroma and arteriolosclerosis.

Diagrams illustrating the string of beads’ angiogram, intimal dysplasia, medial fibroplasia, sub-adventitial fibroplasia, and fibromuscular hyperplasia.

Figure 15.6 Fibromuscular dysplasia and hyperplasia.

These pathological processes, which may occur singly or together, restrict the flow of blood to the renal parenchyma, and ultimately block it completely. When a segmental artery is blocked, there is an infarct of the segment it supplies, and a characteristic atrophy of the full thickness of the cortex and medulla. When smaller branches are occluded, there is a more diffuse loss of parenchyma and an overall shrinkage of the kidney.

The disease progresses over time, and if serial pyelograms have been obtained, one can see the kidneys shrink over the decades (Figure 15.7). This results in a deterioration of renal function and could end with end‐stage renal failure.

Image described by caption.

Figure 15.7 Tracing of X‐rays taken 15 years apart at the age of 66 (left) and 81 (right) in a physician, showing the shrinkage of the kidneys which is seen in old age. (He complained of nocturia but lived to be 92).

15.2.3 Renal Artery Dysplasia

Renal artery dysplasia affects the intima or the media to different degrees. It could be a part of fibromuscular dysplasia that mainly affects the renal and carotid arteries but could also affect different arteries in the body. The intima is affected by patches where it is thickened, alternating with patches where it is unusually thin. This sometimes results in an aneurysmal ballooning of the intima through the wall of the artery. Fibrous tissue is seen just under the adventitia or scattered randomly throughout the entire wall of the artery. The result is to convert the artery from a smooth strong cylinder into an irregular perished pipe, giving an angiographic appearance of a string of beads.

15.2.4 Renal Artery Aneurysm

Renal artery aneurysms are usually diagnosed as an incidental finding during the investigations for other conditions like hypertension or haematuria. Occasionally they could rupture, causing major bleeding particularly during pregnancy [13, 14]. A plain radiograph sometimes shows a characteristic ‘ring’ due to calcification in the wall of the aneurysm (Figure 15.8). The diagnosis is made by colour Doppler sonography, CT angiogram (Figure 15.9), or magnetic resonance imaging (MRI). The kidney on the side of the aneurysm is often smaller than that on the other.

Image described by caption.

Figure 15.8 Pyelogram showing ring of calcification in the wall of the aneurysm.

Image described by caption.

Figure 15.9 (a, b, and c) Computed tomography (CT) angiogram. (d) CT urogram: showing a solitary 3.5‐cm left renal artery aneurysm arising at the point of branching of the renal artery in the hilum of the left kidney calcification seen in the wall of the aneurysm.

Indications for treatment include diameter more than 2.5 cm [15, 16], interval increase in size, hypertension, haematuria, pain and women of child‐bearing age. Treatment options include vascular stent graft or embolisation depending on the position of the aneurysm and its relationship to the renal artery branches as well as the presence of a ‘neck’ [17, 18].

15.2.5 Renal Infarction

Renal infarction is a result of arterial occlusion mainly caused by thrombi, trauma, or polyarteritis nodosa. It is possible for thrombosis process to start in aorta and spread to the renal artery, causing unilateral or bilateral infarcts. It is more common that the small arteries are occluded, resulting in multiple small infarcts. The affected renal parenchyma undergoes necrosis, followed by fibrosis. If these areas are small, this process could be asymptomatic. Sudden, complete renal infarction could present with loin pain and haematuria. The patient could develop ‘epitheluria’, caused by sloughing of renal tubular cells. CT with contrast may aid the diagnosis. DMSA scans will show the silent segment of parenchyma supplied by a segmental artery. When several segmental arteries are occluded, there is a very typical combination of a normal‐appearing retrograde urogram, with a dramatic thinning of the renal parenchyma; however, an angiogram will show arterial occlusion (Figure 15.10).

Image described by caption.

Figure 15.10 This patient had a sudden onset of hypertension, haematuria, and pain in the left loin. The angiogram shows occlusion of the left renal artery, only the upper segmental vessel is spared.

Although immediate surgery has been suggested in the past, anticoagulation and conservative management is usually the first‐line treatment.

15.2.6 Pathogenesis of Renal Hypertension

Renal artery stenosis causes narrowing of the arterial lumen. The lumen of the renal artery must be reduced by some 70% before there is a measurable reduction in blood flow [19], but the pressure gradient across the narrowing segment may be as much as 40 mm Hg [20]. The lowered arterial blood pressure leads to reduction in perfusion pressure, glomerular filtration, and in the amount of sodium that is filtered. As a result, the baroreceptor and macula densa systems release renin [2123]. Renin is the first in a cascade of enzymes which successively liberate the two active polypeptides – angiotensin II and III – from their inactive globulin carrier ‘angiotensinogen’ (Figure 15.11). Both the angiotensins are vasopressors, but in addition, angiotensin II causes the adrenal to produce aldosterone, causing a rise in blood pressure to maintain tissue perfusion. In addition to renal hypertension, ischemic nephropathy can be seen at a later stage, causing deterioration in renal function.

Flow diagram starting from angiotensinogen to angiotension I, to blocked by saralasin, to angiotension II, and to Increases peripheral resistance and Retains Na loses K.

Figure 15.11 The renin‐angiotensin cascade.

The prevalence of renal hypertension is less than 1% of patients with mild or moderate hypertension [24]. Features raising suspicion of this disease include flank pain and diagnosis of hypertension before 30 years of age.

Several diagnostic methods have been used, such as peripheral renin activity assays, captopril testing, and radionuclide renal scanning. These tests have been replaced by Doppler ultrasound, MRI, and CT. Contrast angiography study remains the gold standard for diagnosis.

Medical treatment is the preferred method in the absence of ischaemic changes to the kidney. On the other hand, if patients show signs of progressive obstruction, angioplasty should be considered (Figure 15.12). The results of angioplasty are excellent in patients with fibromuscular hypoplasia.

Diagram illustrating angioplasty, from Guidewire passed through stenosis to Followed by angioplasty balloon, Balloon inflated, and to Stenosis dilated.

Figure 15.12 Angioplasty: the stenosed renal artery is dilated with a balloon.

Surgical revascularisation is rarely used. The block between aorta and renal artery may be bypassed with a graft of saphenous vein or internal iliac artery. On the left side, the splenic artery can be mobilised and anastomosed directly to the renal artery beyond the stenosis [2527]. Nephrectomy is an alternative if the kidney is atrophic with poor function.

15.3 Disorders of the Renal Veins

15.3.1 Congenital Anomalies

Every surgeon should be aware of the retroaortic left renal vein. It is a common anomaly and can cause great difficulty when performing a left nephrectomy for live donor transplantation.

On the right side, a persistent post‐cardinal vein results in a ‘vena cava’ which runs in front of the ureter and causes obstruction. The pyelographic appearances are typical and should contraindicate attempts at percutaneous pyelolysis. The open pyeloplasty is easy, and there is no need to attempt to remove the useless segment of ureter from behind the vena cava.

15.3.2 Renal Vein Thrombosis

Renal vein thrombosis is rare and usually associated with invasion of the renal vein by a tumour, nephrotic syndrome, and membranous glomerulonephritis. The vein becomes occluded causing the kidney to engorge. Patients present with flank pain and haematuria. Examination reveals tender mass. Thrombocytopenia may be noted. Contrast CT scan shows poor uptake of the contrast and a thrombus that may extend to the vena cava. Anticoagulation is usually the first‐line treatment, although thromboembolisation has been reported.

Aug 6, 2020 | Posted by in UROLOGY | Comments Off on Kidney and Ureter Vascular Disorders
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