Ureteropelvic junction obstruction in nephrolithiasis. An etiologic factor

Pelviureteric junction obstruction in adults: A systematic review of the literature

Background

Pelviureteric junction obstruction (PUJO) is a common urological disorder that can present at any stage of life. The underlying etiology in children has been well studied; however, a gap exists in the literature for the adult population. Herein, we performed a systematic review of the literature to evaluate the current evidence on the underlying etiologies of adult patients presenting with PUJO.

Materials and methods

Four electronic databases were searched for relevant studies assessing the underlying etiologies of pelviureteric junction obstruction in adults. Studies were assessed for eligibility based on predefined inclusion and exclusion criteria, and a critical appraisal of methodological quality and risk of bias was performed. Finally, qualitative and quantitative data analyses were performed.

Results

Twelve studies comprising a total of 513 patients with radiologically confirmed PUJO met the inclusion criteria and were included in our analysis. The most common finding was crossing vessels, which were observed in 50.5% of patients, followed by intrinsic ureteral stenosis (27.1%), adhesions (15.3%), and high insertion of the ureter (10.1%).

Conclusions

The underlying etiologies of PUJO in adults remain unclear. This study indicated that obstruction secondary to crossing vessels is the most common cause of obstruction in adults and occurs more frequently than in the pediatric population.

Forming a stone in pelviureteric junction obstruction: Cause or effect?

OBJECTIVES

To investigate a possible causal relationship for stone formation in pelviureteric junction obstruction and to outline management options.

MATERIALS AND METHODS

A literature search and evidence synthesis was conducted via electronic databases in the English language using the key words pelviureteric junction obstruction; urolithiasis; hyperoxaluria; laparoscopic pyeloplasty; flexible nephroscopy; percutaneous nephrolithotomy, alone or in combination. Relevant articles were analysed to extract conclusions.

RESULTS

Concomitant pelviureteric junction obstruction (PUJO) and renal lithiasis has been reported only scarcely in the literature. Although PUJO has been extensively studied throughout the years, the presence of calculi in such a patient has not received equal attention and there is still doubt surrounding the pathophysiology and global management.

CONCLUSIONS

Metabolic risk factors appear to play an important role, enough to justify metabolic evaluation in these patients. Urinary stasis and infection are well known factors predisposing to lithiasis and contribute to some extent. The choice for treatment is not always straightforward. Management should be tailored according to degree of obstruction, renal function, patient symptoms and stone size. Simultaneous treatment is feasible with the aid of minimally invasive operative techniques and laparoscopy in particular.

Ureteropelvic obstruction and renal stones: etiology and treatment

The simultaneous surgical management of ureteropelvic junction obstruction (UPJO) with concomitant renal stones has evolved the last 20 years; hence, the ideal minimally invasive technique is still controversial. Laparoscopic and robot-assisted laparoscopic operations allow precise surgical maneuvers and were thought to simplify the reconstruction steps of the procedure, especially in the treatment of complex cases with large stones. The aim of this study was to summarize the available perioperative and functional outcomes of minimally invasive available techniques. A non-systematic review of the literature was performed using a free-text protocol in the MEDLINE database. The terms used were "ureteropelvic junction obstruction," "renal calculi" and "renal stones." Furthermore, other significant relevant studies cited in the reference lists of the selected papers were also evaluated in the structure of this review. Currently, available evidence suggests that both laparoscopic and robotic-assisted techniques offer excellent surgical solutions in the field of UPJO reconstruction and renal stones removal. In the hands of experienced surgeons, laparoscopic and robotic pyeloplasty with concomitant stone removal is a safe procedure with high stone-free rates and UPJ patency. Minimally invasive pyeloplasty should constitute the first choice of treatment for concomitant renal stones and ureteropelvic junction obstruction.

Treatment outcomes after endopyelotomy performed with or without simultaneous nephrolithotomy: 10-year experience

INTRODUCTION

The incidence of renal calculi associated with ureteropelvic junction obstruction (UPJO) has been reported to be as high as 20%. Although it has been suggested that simultaneous stone removal be performed with endopyelotomy (EP) for patients with UPJO, no crossing vessel, and renal calculi, there are no large series to date reporting in a rigorous fashion the success rate for resolution of the UPJO. This study intends to determine if stone extraction performed with EP increases failure rate.

MATERIALS AND METHODS

A retrospective review was performed for all patients who underwent EP by a single surgeon between August 1996 and November 2006. One hundred forty-six procedures for UPJO were done in 139 patients. Success rate was compared in 105 cases (72%) of isolated UPJO and 41 (28%) cases with UPJO and ipsilateral calculi. Determination of overall success required subjective improvement and objective data based on intravenous pyelogram, computed tomography, and/or nuclear scintigraphy.

RESULTS

Overall success rate was 71% in patients undergoing EP only and 90% in 41 patients who had simultaneous nephrolithotomy (p = 0.04). The odds ratio of failure after EP was 2.9 for severe/massive preoperative hydronephrosis. When considered alone and after adjusting for the severity of preoperative hydronephrosis and/or renal function, simultaneous nephrolithotomy did not increase the EP failure rate.

CONCLUSION

This study demonstrates that UPJO resolves at an equal rate after EP performed with or without ipsilateral renal calculi. Patients with UPJO and renal calculi should undergo stone extraction and EP in the same setting with the expectation of excellent results.

Lithiasis in cystic kidney disease and malformations of the urinary tract

The prevalence of renal stones in renal cystic and malformative conditions exceeds the prevalence of renal stones in the general population, suggesting that the above-mentioned cystic and malformative disorders favor stone formation. Urinary stasis is generally assumed to play a major part in the pathogenesis of the nephrolithiasis associated with distorted renal anatomy due to a delayed washout of crystals and risk of urinary infections. However metabolic factors are also important in the pathogenesis of stones in these conditions. Indeed, metabolic abnormalities have been observed in the majority of stone-forming patients with conditions such as horseshoe kidney and ureteropelvic junction obstruction. Five different models of stone formation can be identified, depending on stone composition, risk of infection stones, and pathogenesis of renal cystic and malformative conditions. A proper metabolic evaluation should be conducted to diagnose specific, treatable metabolic disorders, thereby reducing the frequency of recurrent stone disease in these conditions as well.

Ureteropelvic junction obstruction and coexisting renal calculi in children: role of metabolic abnormalities

OBJECTIVES

To identify the role of metabolic risk factors in the development of renal calculi associated with ureteropelvic junction obstruction (UPJO) in children.

METHODS

A metabolic evaluation, including serum biochemistry and measurement of daily urinary calcium, creatinine, oxalate, citrate, magnesium, urate, and inorganic phosphorus, was carried out in three different populations as follows: UPJO group, 12 children with UPJO and coexisting nephrolithiasis (median age 6 years); calcium stone formation (CSF) group, 90 children with normal urologic anatomy and calcium urolithiasis (median age 7 years); control group, 24 healthy children (median age 7.3 years). The investigation data of the three groups were compared.

RESULTS

The stone composition was calcium oxalate in 9 of the 12 children with UPJO. The investigation data of the UPJO group and CSF group were not significantly different. Both groups differed from the control group in a similar manner. The UPJO and CSF groups excreted more oxalate (P = 0.067 and 0.014, respectively) and less citrate (P = 0.020 and 0.010, respectively) than did the control subjects.

CONCLUSIONS

Abnormal urinary biochemistry seems to have an additional role in the high incidence of nephrolithiasis in children with upper tract anatomic anomalies, and the urinary biochemistry should be screened in such children.

Ureteropelvic junction obstruction and renal calculi. Pathophysiology and implications for management

Ureteropelvic junction (UPJ) obstruction is a well-studied phenomenon in terms of its etiology, implications for renal function, and clinical management. The presence of concomitant ipsilateral calculus disease, however, introduces a confounding variable into the understanding of this entity. This article discusses the relationship between renal calculi and UPJ obstruction as it pertains to their pathophysiology and clinical management as combined entities.

Ureteropelvic junction obstruction in adults

Ureteropelvic junction obstruction (UPJ) in adults is more common than generally appreciated. It may mimic other diseases and may be associated with abdominal pain, hypertension, and recurrent pyelonephritis. Diagnosis and surgical correction were frequently delayed with an average duration of symptoms of 3.2 years for 31 adult patients. Only 4 adults (13%) were diagnosed at the time of their initial onset of symptoms. Nephrectomies were performed on 24 per cent of renal units. Accessory lower pole renal vessels were found in 52 per cent of the adults with UPJ obstruction, twice the rate found in children. Intravenous digital subtraction angiography and diuretic radionucleotide renography should be considered in the evaluation of an adult patient with a UPJ obstruction because of the high rate of accessory vessels. If accessory vessels are present on the contralateral side, especially postnephrectomy, there is heightened concern for the remaining kidney and close follow-up with ultrasonography is recommended.

Directional growth of renal calculi

The forces involved in shaping urinary calculi reside in crystalline characteristics and especially in local influences. Box pleves may restrict passage and, by allowing mobility, help shape a round calculus. Fixation, occurring with a rapidly growing infection stone, facilitates initial growth on a matrix mold in a funnel pelvis, further aided by pelviocaliceal paralysis from bacterial endotoxins and later by stasis. Branched calculi are further shaped by contact with the pelvic and infundibular walls. Through pressure and mucous coating they grow only at the ends. Late caliceal obstruction frees the ends for clubbing. Consideration of these forces aids in prognosis and surgical removal, and may offer opportunities for prevention.