Oxford Handbook of Urology (3 edn)
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Hydronephrosis
Dilatation of the renal pelvis and calyces (Fig. 10.1). When combined with dilatation of the ureters, known as hydroureteronephrosis.
Hydronephrosis as seen on renal ultrasonography.
Obstructive nephropathy is damage to the renal parenchyma, resulting from an obstruction to the flow of urine anywhere along the urinary tract.
Dilatation of the renal pelvis and calyces can occur without obstruction and therefore, hydronephrosis should not be taken to necessarily imply the presence of obstructive uropathy.
Ultrasound
False negative (i.e. obstruction present, no hydronephrosis): acute onset of obstruction; in the presence of an intrarenal collecting system; with dehydration; misdiagnosis of dilatation of the calyces as renal cortical cysts (in acute ureteric colic, ultrasonography fails to detect hydronephrosis in up to 35% of patients with proven acute obstruction on IVU).
False positive (i.e. hydronephrosis, no obstruction): capacious extrarenal pelvis; parapelvic cysts; VUR; high urine flow.
Diagnostic approach to the patient with hydronephrosis
Patients with hydronephrosis may present either as an incidental finding of hydronephrosis on USS or CT done because of non-specific symptoms or it may be identified in a patient with a raised creatinine or presenting with loin pain. Symptoms, if present, will depend on the rapidity of onset of obstruction of the kidney (if that is the cause of the hydronephrosis), whether the obstruction is complete or partial, unilateral or bilateral, and whether the obstruction to the ureter is extrinsic to the ureter or is within its lumen.
History
Severe flank pain suggests a more acute onset of obstruction and if very sudden in onset, a ureteric stone may well be the cause. Pain induced by a diuresis (e.g. following consumption of alcohol) suggests a possible PUJO.
Anuria (the symptom of bilateral ureteric obstruction or complete obstruction of a solitary kidney).
If renal function is impaired, symptoms of renal failure may be present (e.g. nausea, lethargy, anorexia).
Extrinsic causes of obstruction (e.g. compression of the ureters by retroperitoneal malignancy) usually have a more insidious onset whereas intrinsic obstruction (ureteric stone) is often present with severe pain of very sudden onset.
An increase in urine output may be reported by the patient due to poor renal concentrating ability.
Obstruction in the presence of bacterial UTI—signs and symptoms of pyelonephritis (flank pain and tenderness, fever) or sepsis.
Examination
Measure BP: elevated in HPCR due to BPO (caused by fluid overload).
Bilateral oedema (due to fluid overload).
Abdominal examination: percuss and palpate for an enlarged bladder.
DRE (? prostate or rectal cancer) and, in women, vaginal examination (? cervical cancer).
Check serum creatinine to determine the functional effect of the hydronephrosis.
Renal ultrasonography (if not already done).
IVU findings in renal obstruction
An obstructive (dense) nephrogram.
A delay in filling of the collecting system with contrast material.
Dilatation of the collecting system.
An increase in renal size.
Rupture of fornices (junction between renal papilla and its calyx) with urinary extravasation.
Ureteric dilatation and tortuosity.
A standing column of contrast material in the ureter.
Unilateral hydronephrosis
KUB X-ray (a ureteric stone may be seen); CTU (or IVU) if stone suspected.
If no stone seen, but hydronephrosis is confirmed and ureter is non-dilated, the obstruction must be at the PUJ. In the absence of a ureteric stone visible on CTU, the diagnosis must be PUJO.
If no stone seen and the ureter is dilated as well as the kidney, ureteric TCC is likely. Arrange retrograde ureterography to identify site of obstruction and ureteroscopy/ureteric biopsy.
Bilateral hydronephrosis
If the patient is in retention or has a substantial post-void residual urine volume, pass a catheter. If the elevated creatinine falls (and the hydronephrosis improves), the diagnosis is BOO due, for example, to BPH, prostate cancer, urethral stricture, DSD. If the creatinine remains elevated, the obstruction affecting both ureters is higher ‘upstream’.
TRUS and prostatic biopsy if prostate cancer suspected on DRE, CT scan looking for malignant bilateral ureteric obstruction, AAA.
Obstructing ureteric stone.
PUJO.
Obstructing clot in ureter.
Obstructing ureteric TCC.
(Any of the causes listed below where the pathologic process has not yet extended to involve both ureters).
BOO.
BPH.
Prostate cancer.
Urethral stricture.
DSD.
Posterior urethral valve.
Bilateral ureteric obstruction at their level of entry into the bladder.
Locally advanced cervical cancer.
Locally advanced prostate cancer.
Locally advanced rectal cancer.
Poor bladder compliance (often combined with DSD): neuropathic bladder (spinal cord injury, spina bifida), post-pelvic radiotherapy.
Periureteric inflammation.
From adjacent bowel involved with inflammatory bowel disease (e.g. Crohn’s, ulcerative colitis) or diverticular disease.
Retroperitoneal fibrosis.
Idiopathic (diagnosed following exclusion of other causes).
Periarteritis—aortic aneurysm, iliac artery aneurysm.
Post-irradiation.
Drugs—methysergide, hydralazine, haloperidol, LSD, methyldopa, beta blockers, phenacetin, amphetamines.
Malignant—retroperitoneal malignancy (lymphoma, metastatic disease from, e.g. breast cancer), post-chemotherapy.
Chemicals—talcum powder.
Infection—TB, syphilis, gonorrhoea, chronic UTI.
Sarcoidosis.
Bilateral PUJO (uncommon).
Hydronephrosis of pregnancy (partly due to smooth muscle relaxant effect of progesterone, partly obstruction of ureters by fetus).
Hydronephrosis in association with an ileal conduit (a substantial proportion of patients with ileal conduit urinary diversion has bilateral hydronephrosis in the absence of obstruction).
Bilateral ureteric stones (rare).
Management of ureteric strictures (other than PUJO)
Definition
A normal ureter undergoes peristalsis and therefore, at any one moment, at least one area of the ureter will be physiologically narrowed. A ureteric stricture is a segment of ureter that is narrowed and remains so on several images (i.e. it is a length of ureter that is constantly narrow).
Causes
Most ureteric strictures are benign and iatrogenic. Some follow the impaction of ureteric stone for a prolonged period; malignant strictures—within wall of ureter (e.g. TCC ureter), extrinsic compression from outside wall of ureter (e.g. lymphoma, malignant retroperitoneal lymphadenopathy); retroperitoneal fibrosis (RPF) which may be benign (idiopathic, aortic aneurysm, post-irradiation, analgesic abuse) or malignant (retroperitoneal malignancy, post-chemotherapy).
Mechanism of iatrogenic ureteric stricture formation
Normally ischaemic:
Usually injury at time of open or endoscopic surgery (e.g. damage to ureteric blood supply or direct damage to the ureter at time of colorectal resection, AAA graft, hysterectomy); at ureteroscopy—mucosal trauma (from ureteroscope or electrohydraulic lithotripsy), perforation of ureter (urine extravasation, leading to fibrosis).
Radiotherapy in the vicinity of the ureter.
Stricture of ureteroneocystostomy of renal transplant.
Investigations
The stricture may be diagnosed following investigation for symptoms (loin pain, upper tract infection) or may be an incidental finding on an investigation done for some other reason. The stricture may be diagnosed on renal USS (hydronephrosis), IVU, or CTU. A MAG3 renogram will confirm the presence of obstruction (some minor strictures may cause no renal obstruction) and establish split renal function. Where ureteric TCC is possible, proceed with ureteroscopy and biopsy.
‘Treatment’ options
Nothing (symptomless stricture in an old patient with significant comorbidity or <25% function in an otherwise healthy patient with a normally functioning contralateral kidney).
Permanent JJ stent or nephrostomy, changed at regular intervals (symptomatic stricture in an old patient with significant comorbidity or <25% function in affected kidney with compromised overall renal function).
Incision + balloon dilatation (endoureterotomy by Acucise® balloon; ureteroscopy or nephrostomy and incision, e.g. by laser). Leave a 12 Ch stent for 4 weeks.
Excision of stricture and repair of ureter (open or laparoscopic approach).
Nephrectomy.
Balloon dilatation of a lower ureteric stricture.
The catheter used for balloon dilatation.
Factors associated with reduced likelihood of a good outcome after endoureterotomy
<25% function in kidney.
Stricture length >1cm.
Ischaemic stricture.
Midureteric stricture (compared with upper and lower)—tenuous blood supply.
JJ stent size <12 Ch.
Ureteroenteric strictures (ileal conduits, ureteric implantation into neobladder)
These are due to ischaemia and/or periureteral urine leak in the immediate post-operative period, which leads to fibrosis in the tissues around the ureter. In ileal conduits, the left ureter is affected more than the right because greater mobilization is required to bring it to the right side and it may be compressed under the sigmoid mesocolon, both of which impair blood flow to the distal end of the ureter.
Pathophysiology of urinary tract obstruction
Effects of obstruction on renal blood flow and ureteric pressure
Acute unilateral ureteric obstruction (UUO)
Leads to a triphasic relationship between renal blood flow (RBF) and ureteric pressure.
Phase 1 (up to 1.5h post-obstruction): ureteric pressure rises, RBF rises (afferent arteriole dilatation).
Phase 2 (from 1.5–5h post-obstruction): ureteric pressure continues to rise, RBF falls (efferent arteriole vasoconstriction).
Phase 3 (beyond 5h): ureteric pressure falls, RBF continues to fall (afferent arteriole vasoconstriction).
Acute bilateral ureteric obstruction (BUO) or obstruction of a solitary kidney
Phase 1 (up to 1.5h post-obstruction): ureteric pressure rises, RBF rises (afferent arteriole dilatation).
Phase 2 (from 1.5–5h post-obstruction): ureteric pressure continues to rise, RBF is significantly lower than that during UUO.
Phase 3 (beyond 5h): ureteric pressure remains elevated (in contrast to UUO). By 24h, RBF has declined to the same level for both UUO and BUO.
In UUO, the decrease in urine flow through the nephron results in a greater degree of Na absorption so Na excretion falls. Water loss from the obstructed kidney increases.
Release of BUO is followed by a marked natriuresis, increased K excretion, and a diuresis (a solute diuresis).This is due to:
An appropriate (physiological) natriuresis to excrete excessive Na which is a consequence of BUO.
A solute diuresis from the accumulation of urea in ECF.
A diminution of the corticomedullary concentration gradient, which is normally established by the countercurrent mechanism of the Loop of Henle, and is dependent on maintenance of flow through the nephron—reduction of flow, as occurs in BUO, reduces the efficiency of the countercurrent mechanism (effectively, the corticomedullary concentration gradient is ‘washed out’).
There may also be accumulation of natriuretic peptides (e.g. ANP) during BUO, which contributes to the natriuresis following release of the obstruction.
Likelihood of recovery of renal function after release of obstruction
In dogs with completely obstructed kidneys, full recovery of renal function after 7 days of UUO occurs within 2 weeks of relief of obstruction. A total of 14 days of obstruction leads to a permanent reduction in renal function to 70% of control levels (recovery to this level taking 3–6 months after reversal of obstruction). There is some recovery of function after 4 weeks of obstruction, but after 6 weeks of complete obstruction, there is no recovery. In humans, there is no clear relationship between the duration of BUO and the degree of recovery of renal function after relief of obstruction.
Physiology of urine flow from kidneys to bladder
Urine production by the kidneys is a continuous process. Its transport from the kidneys down the ureter and into the bladder occurs intermittently by waves of peristaltic contraction of the renal pelvis and ureter (peristalsis = wave-like contractions and relaxations). The renal pelvis delivers urine to the proximal ureter. As the proximal ureter receives a bolus of urine, it is stretched and this stimulates it to contract while the segment of ureter just distal to the bolus of urine relaxes. Thus, the bolus of urine is projected distally.
The origin of the peristaltic wave is from collections of pacemaker cells in the proximal most regions of the renal calyces. In species with multiple calyces such as humans, there are multiple pacemaker sites in the proximal calyces. The frequency of contraction of the calyces is independent of urine flow rate (it is the same at high and low flow rates) and it occurs at a higher rate than that of the renal pelvis. Precisely how the frequency of contraction of each calyx is integrated into a single contraction of the renal pelvis is not known. All areas of the ureter are capable of acting as a pacemaker. Stimulation of the ureter at any site produces a contraction wave that propagates proximally and distally from the site of stimulation, but under normal conditions, electrical activity arises proximally and is conducted distally from one muscle cell to another (the proximal most pacemakers are dominant over these latent pacemakers).
Peristalsis persists after renal transplantation and denervation and does not, therefore, appear to require innervation. The ureter does, however, receive both parasympathetic and sympathetic innervation and stimulation of these systems can influence the frequency of peristalsis and the volume of urine bolus transmitted.
At normal urine flow, the frequency of calyceal and renal pelvic contractions is greater than that in the upper ureter and there is a relative block of electrical activity at the PUJ. The renal pelvis fills; the ureter below it is collapsed and empty. As renal pelvic pressure rises, urine is extruded into the upper ureter. The ureteric contractile pressures that move the bolus of urine are higher than renal pelvic pressures. A closed PUJ may prevent back-pressure on the kidney. At higher urine flow rates, every pacemaker-induced renal pelvic contraction is transmitted to the ureter.
To propel a bolus of urine, the walls of the ureter must coapt (touch). Resting ureteric pressure is 0–5cmH2O and ureteric contraction pressures range from 20 to 80cmH2O. Ureteric peristaltic waves occur 2–6 times per min. The VUJ acts as a one-way valve under normal conditions, allowing urine transport into the bladder and preventing reflux back into the ureter.
Ureter innervation
Autonomic:
the ureter has a rich autonomic innervation.
Sympathetic: preganglionic fibres from spinal segments T10–L2; post-ganglionic fibres arise from the coeliac, aorticorenal, mesenteric, superior, and inferior hypogastric (pelvic) autonomic plexuses.
Parasympathetic: vagal fibres via coeliac to upper ureter; fibres from S2–4 to lower ureter.
The role of ureteric autonomic innervation is unclear. It is not required for ureteric peristalsis (though it may modulate this). Peristaltic waves originate from intrinsic smooth muscle pacemakers located in minor calyces of the renal collecting system.
Afferent
Upper ureter—afferents pass (alongside sympathetic nerves) to T10–L2; lower ureter—afferents pass (alongside sympathetic nerves and by way of the pelvic plexus) to S2–4. Afferents subserve stretch sensation from the renal capsule, collecting system of kidney (renal pelvis and calyces), and ureter. Stimulation of the mucosa of the renal pelvis, calcyes, and ureter also stimulates nociceptors, the pain so felt being referred in a somatic distribution to T8–L2 (kidney T8–L1, ureter T10–L2), in the distribution of the subcostal, iliohypogastric, ilioinguinal, or genitofemoral nerves. Thus, ureteric pain can be felt in the flank, groin, scrotum or labia, and upper thigh, depending on the precise site in the ureter from which the pain arises.
Retroperitoneal fibrosis
Retroperitoneal fibrosis (RPF) was first clearly described by the French urologist Albarran in 1905. Further cases were described by Ormond in 1948.
Benign causes
Autoimmune: Idiopathic RPF (periaortitis) comprises two-thirds of cases. Considered to be a response to an insoluble lipid called ceroid that has leaked through a thinned arterial wall from atheromatous plaques, a fibrous plaque extends laterally and downwards from the renal arteries encasing the aorta, inferior vena cava and ureters, but rarely extends into the pelvis. The central portion of the plaque consists of woody scar tissue, while the growing margins have the histological appearance of chronic inflammation. It may be associated with abdominal aortic aneurysm (AAA), intra-arterial stents, and angioplasty; mediastinal, mesenteric, or bile-duct fibrosis.
Drugs including methysergide, beta-blockers, hydralazine, haloperidol, amphetamines, and LSD; methyl methacrylate cement used for joint replacement.
Chronic urinary infection including TB.
Inflammatory conditions such as Crohn’s disease, Reidel’s thyroiditis, or sarcoidosis.
Amyloidosis and periaortic haematoma may mimic RPF.
Malignant causes
Lymphoma is the most common cause, also sarcoma.
Metastatic or locally infiltratative carcinoma of the breast, stomach, pancreas, colon, bladder, prostate, and carcinoid tumours.
Radiotherapy may cause RPF, although rare in recent years with precise field localization.
Chemotherapy, especially following treatment of metastatic testicular tumours, may leave fibrous masses encasing the ureters. These may or may not contain residual tumour.
Presentation
Idiopathic retroperitoneal fibrosis classically occurs in the fifth or sixth decade of life.
Men are affected twice as commonly as women.
In the early stage, symptoms are relatively non-specific, including loss of appetite and weight, low-grade fever, sweating, and malaise. Lower limb swelling may develop. Dull, non-colicky abdominal or back pain is described in up to 90% of patients.
Later, the major complication of the disease develops: bilateral ureteric obstruction, causing anuria and renal failure.
Examination may reveal hypertension in up to 60% of patients and an underlying cause such as an abdominal aortic aneurysm.
Investigations
Inflammatory serum markers are elevated in idiopathic RPF (60–90% elevated ESR).
Pyuria or bacteriuria are common.
Ultrasound will demonstrate uni- or bilateral hydronephrosis.
CT, IVU, or ureterography reveal tapering medial displacement of the mid-ureters with proximal dilatation and will exclude calculus disease. Up to one third of patients will have a non-functioning kidney at the time of presentation due to long standing obstruction.
CT-guided fine needle biopsy of the mass may confirm the presence of malignant disease or infection. A negative result does not exclude malignancy.
Management
Emergency management of a patient presenting with established renal failure requires relief of the obstruction by percutaneous nephrostomy or ureteric stenting.
Replacement of fluid and electrolyte losses following relief of bilateral ureteric obstruction is vital due to the frequent post-obstructive diuresis.
Assess with daily weighing and measurement of blood pressure lying and standing.
Steroids may decrease the oedema often associated with retroperitoneal fibrosis and in this way help reduce the obstruction. If used, they are usually discontinued when inflammatory markers return to normal. Azathioprine, tamoxifen, and cyclophosphamide have been used successfully in some patients.
Surgical ureterolysis with omental wrap is often necessary to free and insulate the ureters from the encasing fibrous tissue.
Monitor for recurrent disease with serum creatinine and ultrasound 3–6 monthly or annual DMSA renography for 5y.
