Overview
Definition:
Anderson-Hynes pyeloplasty is a surgical procedure to relieve obstruction at the ureteropelvic junction (UPJ), the point where the renal pelvis narrows to become the ureter
It involves excising the obstructed segment of the renal pelvis and ureter and then performing a dismembered pyeloplasty, typically using a dismembered flap (e.g., Flank flap or Davis intubated) to reconstruct the UPJ, ensuring a tension-free anastomosis
This is the most common surgical treatment for symptomatic UPJ obstruction.
Epidemiology:
Ureteropelvic junction obstruction is the most common cause of congenital hydronephrosis in children, with an incidence of approximately 1 in 1,500 live births
It can be unilateral or bilateral and affects males slightly more than females
While often congenital, it can also be acquired later in life due to factors such as stones, strictures, or extrinsic compression.
Clinical Significance:
Untreated UPJ obstruction can lead to progressive renal damage, secondary infection, stone formation, and flank pain
Early diagnosis and effective surgical intervention, such as Anderson-Hynes pyeloplasty, are crucial for preserving renal function, preventing complications, and improving the patient's quality of life
It is a cornerstone procedure in pediatric urology and frequently tested in surgical residency examinations.
Indications
Absolute Indications:
Symptomatic UPJ obstruction confirmed by imaging and diuretic renography showing poor drainage
Progressive hydronephrosis
Renal stones associated with UPJ obstruction
Hypertension secondary to UPJ obstruction.
Relative Indications:
Asymptomatic but significant hydronephrosis with poor differential renal function (<40%) on diuretic renography
Recurrent urinary tract infections in patients with demonstrable UPJ obstruction
Management of solitary kidney with UPJ obstruction.
Contraindications:
Poorly functioning kidney with irreversible damage (nephrectomy may be considered)
Uncorrectable or other significant comorbidities that make surgery high-risk
Absence of obstruction on serial imaging and renography.
Diagnostic Approach
History Taking:
Key historical points include flank or abdominal pain (often intermittent, colicky), nausea and vomiting, urinary tract infections (especially in children), hematuria, and failure to thrive
A detailed family history may reveal similar conditions.
Physical Examination:
Physical examination may reveal a palpable abdominal mass (rare), costovertebral angle tenderness, or signs of infection
In infants, a palpable mass may be present
General physical examination is important to assess overall health and identify any comorbidities.
Investigations:
Initial assessment often includes urinalysis and urine culture to rule out infection
Ultrasound is typically the first imaging modality to assess hydronephrosis
Intravenous urography (IVU) or computed tomography urography (CTU) can delineate the obstruction
Diuretic renography (e.g., Tc-99m MAG3 scan) is crucial for assessing renal function and drainage, quantifying obstruction, and determining the need for intervention
Differential renal function (DRF) is a key parameter
Delayed transit and poor efflux on renography are indicative of significant obstruction.
Differential Diagnosis:
Other causes of hydronephrosis include ureteral calculi, ureteral strictures (post-infectious, post-traumatic), neurogenic bladder, posterior urethral valves (in males), vesicoureteral reflux (VUR), and extrinsic compression of the ureter
Distinguishing UPJ obstruction from these conditions is essential.
Surgical Management
Preoperative Preparation:
Patients should be adequately hydrated
Broad-spectrum antibiotics are administered perioperatively
Imaging review is critical, ensuring all necessary scans are available
In children, an indwelling Foley catheter may be placed prior to surgery
Adequate pain control is essential.
Operative Technique:
The Anderson-Hynes technique is a dismembered pyeloplasty
A curvilinear incision is made in the flank or anteriorly
The renal pelvis and proximal ureter are identified
The obstructed segment of the renal pelvis and the narrowed portion of the proximal ureter are excised
A common variation involves creating a dependent flap of the renal pelvis to ensure better drainage
The ureter is spatulated to create a wider opening
The renal pelvis is then reconstructed over a splint (e.g., ureteral stent) to ensure patency
The anastomosis is typically performed in a Y-V or U-V fashion
Careful attention is paid to achieve a tension-free, watertight anastomosis
Laparoscopic and robotic approaches are increasingly common and offer similar outcomes with shorter recovery times.
Intraoperative Considerations:
Identification and preservation of the renal artery and vein are critical
Adequate exposure of the UPJ is paramount
The stent placement should facilitate drainage and prevent kinking of the ureter
Careful watertight closure of the renal pelvis is important to prevent urinoma
A nephrostomy tube or indwelling ureteral stent is typically placed for drainage
A drain may be placed in the retroperitoneum.
Postoperative Care:
Postoperative care includes monitoring of urine output, fluid balance, pain management, and early mobilization
The drain and stent are typically removed after 3-7 days, depending on urine output and visualization of the anastomosis
Intravenous antibiotics may be continued
Oral intake is gradually advanced
Pain management is crucial, often involving opioids initially, transitioning to oral analgesics
Close monitoring for signs of infection, bleeding, or urine leak is vital.
Complications
Early Complications:
Urine leak (urinoma)
Bleeding
Infection (wound or systemic)
Ileus
Stent migration or blockage
Injury to adjacent organs.
Late Complications:
Stenosis at the anastomosis
Recurrence of UPJ obstruction
Stone formation in the renal pelvis
Chronic flank pain
Persistent hydronephrosis
Renal insufficiency.
Prevention Strategies:
Meticulous surgical technique, including tension-free anastomosis and adequate spatulation of the ureter
Careful placement and secure fixation of ureteral stents
Aggressive infection control
Proper patient selection and thorough preoperative assessment
Postoperative monitoring for signs of complications.
Prognosis
Factors Affecting Prognosis:
Preoperative differential renal function
Degree of hydronephrosis
Technical success of the surgical repair
Absence of complications
Age of the patient
Presence of associated anomalies.
Outcomes:
The success rate of Anderson-Hynes pyeloplasty is high, typically exceeding 90-95% for primary repairs
Symptom relief is usually significant, and preserved or improved renal function is expected in most cases
Long-term renal salvage rates are excellent when performed effectively.
Follow Up:
Postoperative follow-up typically involves serial renal ultrasounds to assess hydronephrosis and assess improvement in the collecting system
Diuretic renography may be repeated at 3-6 months to confirm adequate drainage and assess differential renal function
Patients are generally followed long-term, especially in pediatric cases, to monitor for recurrent obstruction or renal deterioration.
Key Points
Exam Focus:
The Anderson-Hynes pyeloplasty is the gold standard for UPJ obstruction
Key points include indications, the dismembered technique, intraoperative considerations (stenting, spatulation), common complications (urine leak, restenosis), and prognostic factors like preoperative DRF
Laparoscopic/robotic alternatives are important.
Clinical Pearls:
Ensure adequate spatulation of the ureter to create a wide lumen for anastomosis
A dependent flap of the pelvis can help prevent dependent pooling of urine
Proper stent management is crucial for preventing early complications
Remember to assess differential renal function pre-operatively as a prognostic indicator.
Common Mistakes:
Performing a tension-filled anastomosis
Inadequate spatulation of the ureter
Failure to adequately excise the obstructed segment
Inappropriate stent placement or removal
Misinterpreting diuretic renography findings
Not considering acquired causes of UPJ obstruction.