Pelvi-ureteric junction obstruction:overview

Ureteropelvic junction (UPJ) obstruction is defined as an obstruction of the flow of urine from the renal pelvis to the proximal ureter.





UPJ obstruction is the most common cause of neonatal and antenatal hydronephrosis, occurring in 1 per 1500 live births. 50% of patients diagnosed with antenatal hydronephrosis are eventually diagnosed with UPJ obstruction upon further workup.

PATHOPHYSIOLOGY:
Congenital UPJ obstruction most often results from intrinsic disease. A frequently found defect is the presence of an aperistaltic segment of the ureter, perhaps similar to that found in primary obstructive megaureter. In these cases, histopathologic studies reveal that the spiral musculature normally present has been replaced by abnormal longitudinal muscle bundles or fibrous tissue.
Other causes
A. An abnormal or high insertion of the ureter into the renal pelvis may affect drainage of urine. This may be an effect rather than a cause in some cases.
B. Crossing lower-pole renal vessel may result in pressure on the ureter by a vessel can prohibit urinary flow down the ureter.(cause and effect relationship not clear).
C. Rotation of the kidney and renal hypermobility can cause intermittent obstruction
D. Secondary UPJ obstruction can be caused by prior surgical intervention to treat other disorders (or failed repair of a primary UPJ obstruction (recurrent pelvi-ureteric junction obstruction). It is usually secondary to periureteral scar formation.


Problem
UPJ obstruction is defined as an obstruction of the flow of urine from the renal pelvis to the proximal ureter. The resultant back pressure within the renal pelvis may lead to progressive renal damage and deterioration.
UPJ obstruction presents most frequently in childhood, but adults and elderly individuals can also present
Frequency
• UPJ obstruction is found in approximately 50% of patients diagnosed with antenatal hydronephrosis.
• The male-to-female ratio of UPJ obstruction is 3-4:1.
• In general, the left kidney is more commonly affected than the right kidney.
• UPJ obstruction manifests bilaterally in 10% cases.
Presentation:

Neonates who present with hydronephrosis should be fully evaluated with voiding cystourethrography (VCUG; to rule out vesicoureteral reflux) and renal ultrasonography soon after birth.
If renal ultrasonography demonstrates hydronephrosis without reflux on VCUG, a diuretic renal scan should be performed to quantify relative renal function and to define the extent of obstruction.



Renal pelvic dilatation in a case of Pelvi-Ureteric Junction Obstruction



Micturating Cysto-Urethrography showing no reflux mandatory step before surgical therapy

Older children may present with UTI, a flank mass, or intermittent flank pain
Adults with UPJ obstruction can present with various symptoms, including back and flank pain, UTI, and/or pyelonephritis.
A detailed history may reveal that the pain correlates with periods of increased fluid intake or ingestion of a food with diuretic properties (ie, Dietl crisis, beer drinkers kidney).
Indications
The goals in treating patients with ureteropelvic junction (UPJ) obstruction are to improve renal drainage and to maintain or improve renal function.
As mentioned above, dilatation of the intrarenal collecting system or hydronephrosis does not necessarily imply obstruction. Specifically in children, renal pelvic dilatation should be monitored with serial imaging to assess for changes in dilatation, renal parenchymal thickness and/or the presence of scarring, and function(Renal ultrasonography and renal scintigraphy). Surgical repair is indicated upon a significant differential on serial imaging or progressive deterioration of renal function.
Similarly, in adults, repair is recommended if nuclear medicine renal scan(deteriorating on serial scan or deteriorated function on initial scan)or intravenous pyelography (IVP) reveals ureteral obstruction.
Relevant Anatomy

The evaluation of an obstructed ureteropelvic junction (UPJ) requires information about ureteral and surrounding anatomy, renal position and ectopy, associated vasculature, and renal function.
Prior to surgical intervention, the surgeon frequently evaluates for renal position/ectopy, mobility, and UPJ anatomy, such as high-insertion variants versus annular stricture variants.
The major vascular supply of the UPJ comes from branches of the renal artery. These vessels usually lie in an anteromedial location in relation to the proximal ureter. Aberrant polar vessels may also be associated with the renal pelvis, causing compression and obstruction of the collecting system. These vessels arise from either the renal artery from a position proximal to the main intrarenal branching site or directly from the aorta. They can surround the UPJ and can be associated with obstruction, or they may be aberrantly positioned secondary to increasing hydronephrosis.
The vascular anatomy at the UPJ becomes crucial during an endopyelotomy. The renal collecting system may be accessed percutaneously (antegrade) or in a retrograde fashion via passage of a ureteroscope through the urethra. While most associated UPJ vessels lie in the anteromedial plane, accessory vessels may lie posteriorly or laterally. If all endoscopic incisions are made in the posterior-lateral plane, intraoperative hemorrhage may occur. For this reason, a comprehensive vascular evaluation with complemented CT angiography is needed. CT scanning in combination with 3-phase and 3-dimensional contrast imaging yields a reported sensitivity of around 80% in revealing crossing vessels.



When an open or laparoscopic pyeloplasty is performed, an accurate understanding of the vascular anatomy allows the surgeon to preserve the accessory renal vessels and to redirect them if the surgeon feels that they contribute to the obstruction. If an endopyelotomy is planned, this information can guide the surgeon in directing the endopyelotomy incision away from crossing vessels.
Retrograde pyelography at the time of surgery is often used to estimate the length of the stricture and the amount of pelvis/ureter that needs to be excised at the time of the pyeloplasty to create a dependent funnel
Laboratory Studies
• All patients with possible ureteropelvic junction (UPJ) obstruction should be evaluated routine hematological and biochemical tests along with urinalysis.
Imaging Studies
• Renal ultrasonography and VCUG are performed in children with suspected UPJ obstruction.
• IVP is used to evaluate patients with possible UPJ obstruction. However, in the evaluation of a child with a hydronephrotic kidney, diuretic renography has taken the place of IVP. The benefits of diuretic renography are that iodine-based intravenous contrast is not used, radiation exposure is minimal, and renal function can be better quantified. The disadvantage of the nuclear medicine scan is that insight into renal anatomy is not obtained(especially many urologists are used to IVP rather than even CT reconstructed images for taking decisions regarding renal surgery for example-percutaneous nephrolithotomy).





IVP showing right pelvi-ureteric junction obstruction

• Functionally significant obstruction is often diagnosed with diuretic renal scanning. The conventional renographic criteria include a flat or rising washout curve after diuretic with T 1/2 of greater than 20 minutes and differential function of less than 40. The differential function is important in determining the need for intervention, especially in asymptomatic patients, and in selecting the appropriate treatment (pyeloplasty vs nephrectomy). Poorly functioning kidneys (<10%) are often best treated with nephrectomy. Nuclear medicine scanning is also used to assess outcomes after surgical intervention. The scans are best interpreted by combination of nuclear consultant and urologist as sometimes the sheer size of the pelvis and kidney can overestimate the function of the kidney. Also after the surgery situation may arise that the kidney size will decrease because of removal of excess of pelvis and removal of obstruction resulting in decreasing in relative function(not representative) so patients attendants and the patient should be counseled pre-operatively.



Renal scan showing obstructed kidney

• Sometimes in a patient the scan may come up with the equivocal findings in such situations the scan can be repeated with different protocoal(prior loading with diuretic so called F- protocol)
•
Medical Therapy

In children with ureteropelvic junction (UPJ) obstruction, GOAL is focused on maintaining sterile urine and assessing renal function and the degree of hydronephrosis. Typically, when imaging studies reveal an incomplete obstruction, the patient is monitored with routine renal ultrasonography and nuclear medicine renography.
Currently, medical therapy is unavailable for the treatment of both adult and pediatric cases of UPJ obstruction.
Initially, most children are treated conservatively and monitored closely. Intervention is indicated in the event of significantly impaired renal drainage or poor renal growth. The accepted criteria for intervention in infants and children include T 1/2 greater than 20 minutes, differential function less than 40%, and ongoing parenchymal thinning with or without contralateral compensatory hypertrophy(indicating the ipsilateral kidney atrophy) . Intervention is also indicated in those with pain, hypertension, hematuria, secondary renal calculi, and recurrent UTIs.( a word of caution –pain may not always be alleviated in renal surgery .The patient will need counseling regarding this prior)
Surgical Therapy

Surgical intervention to treat an obstructed UPJ is warranted, especially upon deterioration of renal function.
The principles of surgical repair, as initially described by Foley, include the following:
• Formation of a funnel
• Dependent drainage
• Watertight anastomosis
• Tension-free anastomosis





In children, the procedure of choice is an Anderson-Hynes dismembered pyeloplasty. The approach may be performed through a flank, dorsal lumbotomy, or anterior extraperitoneal technique. Laparoscopy has gained increasing acceptance in pediatric surgery and is often used to perform pyeloplasties in children. In many cases, laparoscopic pyeloplasty is technically unfeasible in very small children and infants because of space constraints. Using this method, the obstructed segment is completely resected, with reanastomosis of the renal pelvis and ureter in a dependent funneled fashion. The decision of whether to use a ureteral stent transiently during the initial healing process is based on the personal preference of the surgeon. The success rate of dismembered pyeloplasty for treating an obstructed UPJ exceeds 95%.

Open pyeloplasty leaves behind scar.Increased hospitalisation ,pain and delay in recuperation are the other problems.


Laparoscopic pyeloplasty offers a minimally invasive treatment option that may be used in patients with either primary or secondary UPJ obstruction and is emerging as a new criterion standard in the treatment of UPJ obstruction. Success rates are comparable with those of open pyeloplasty procedures, and some studies have shown that laparoscopy offers the advantages of decreased morbidity, shorter hospital stay, and quicker recovery. Laparoscopic pyeloplasty is a technically demanding procedure that generally requires significant laparoscopic experience. Robotic-assisted laparoscopic pyeloplasty has become increasingly popular as the robots have become more prevalent. A small intrarenal pelvis is a relative contraindication to laparoscopic pyeloplasty as the intrarenal dissection would pose difficulty for the laparoscopic surgeon.
Endoscopic treatment alternatives include an antegrade or retrograde endopyelotomy, which is an endoscopic incision performed through the obstructing segment.
Prior to incising a UPJ obstruction, imaging study(CT angiography) is recommended to evaluate adjacent ureteral vasculature.An endopyelotomy incision is performed through the area of obstruction with a laser, electrocautery, or endoscopic scalpel. Most surgeons dilate the newly incised area with a balloon catheter to help ensure a complete incision. This is followed by prolonged ureteral stenting, for a period of 4-8 weeks. The stent acts as internal scaffolding during healing and maintains renal drainage. Success rates with the percutaneous and ureteroscopic endopyelotomy are 80-90%.
When open pyeloplasty fails, endopyelotomy is particularly useful, even in the pediatric population.
In patients who have a suboptimal result from endopyelotomy, repeat incision can be performed with success. Traditional open or laparoscopic pyeloplasty is also indicated after failed endopyelotomy.
Of the open surgical repairs used to treat UPJ obstruction, the Anderson-Hynes dismembered pyeloplasty is particularly useful for the high-insertion variant. The benefit of this procedure is complete excision of the diseased segment of ureter and reconstruction with healthy viable tissue.

Spiral and vertical flaps (eg, Culp and DeWeerd, Scardino and Prince) are useful when a long-strictured segment of diseased ureter is encountered. With these procedures, the proximal ureter is re-created with redundant renal pelvis that is tubularized.
Ureterocalicostomy, ie, anastomosis of the ureter to a lower-pole renal calyx, is usually reserved for failed open pyeloplasty when no extrarenal pelvis and significant hilar scarring are present.It also is convenient to perform the procedure in thinned out parenchyma.
Robotic-assisted laparoscopic pyeloplasty




This procedure is particularly helpful in the surgeon who is learning the laparoscopic technique. The da Vinci robotic surgical system has been used successfully for laparoscopic reconstruction. It offers several advantages to surgeons unskilled in laparoscopy, including increased degrees of suturing freedom(just like movement of the wrist), stereoscopic vision, tremor filtration, precision and maneuvreability. The results are similar to those of conventional laparoscopic pyeloplasty.
Follow-up

Prophylactic antibiotic therapy should be given postoperatively. Remove the endopyelotomy stent after 4-8 weeks.
Follow up with renal ultrasonography 1-3 months after surgery. In addition, follow up with IVP or nuclear medicine renal scan 3-6 months after surgery.
Serial renal imaging is recommended for the first year after surgery and should be continued less frequently thereafter if results have normalized.
Complications

Potential complications from open surgical pyeloplasty include UTI and pyelonephritis, urinary extravasation and leakage, recurrent ureteropelvic junction (UPJ) obstruction, or stricture formation. Treatment of urinary leakage is centered around catheter drainage, such as nephrostomy, ureteral stent, or perianastomotic drain, to direct urine away from the perianastomotic tissues and to decrease the risk of postoperative stricture disease.
Specific complications from endopyelotomy include significant intraoperative bleeding if the endoscopic incision is made inadvertently into a major polar vessel, postoperative infection, and recurrence of obstruction. If significant intraoperative bleeding is encountered with hypotension, emergency arteriography and embolization are indicated.