Etiology of Hydronephrosis in adults and children: Ultrasonographic Assessment in 233 patients

Objectives: Hydronephrosis (HN) is dilatation of the collecting system of the kidney due to obstruction of urine outflow. This study intended firstly, to investigate the efficacy of ultrasound (US) imaging to determine the cause of HN, and secondly, to list the causes of HN. Methods: In this retrospective study, 233 patients with HN were scanned to determine the cause of the HN in the period from 1st January 2016 to 31st October 2017. Categorical results were written as frequencies and percentages. Results: Out of 233, 91.41% were adults and 8.58% were children (P<0.001), 66.10% were male and 33.90% were female (P<0.001). In 55.36%, HN was in the right kidney and 44.64% was in the left (P=0.116). Exactly 58% of patients were suffering from grade-2, 21.5% grade-3, 11.6% grade-1, and 8.2% grade-4 HN. US imaging can determine the cause of HN in 70.4% of patients. Kidney or ureteric calculi were the cause of HN in 54.1% of cases, reflux was in 7.3%, and pelviureteric junction (PUJ) stenosis was in 3.9%. In cases of calculi induced HN, 25.3% of the calculi were in the vesicoureteric (VUJ) junction, 21.5% were in the renal pelvis, 6.4% were in the PUJ or upper ureter, and only 0.9% were in the middle ureter. Conclusion: Ultrasound imaging can determine the cause of HN in more than two thirds of patients. Calculi are the most common cause of HN even in children and are most common in the VUJ junction.


INTRODUCTION
Hydronephrosis (HN) is dilatation of the renal collecting system of the kidney due to obstruction of urine outflow in any part of the urinary tract. It can present solely or together with dilatation of the ureter in an entity called hydroureternephrosis. HN can present as unilateral or bilateral, acute or chronic at any age. 1 According to the Society of Fetal Urology (SFU) classification system, HN is classified into four grades; Grade-1; dilatation of the renal pelvis only. Grade-2; dilatation of the renal pelvis and major calyces. Grade-3; dilatation of the renal pelvis and major and minor calyces. Grade-4; dilatation of the renal pelvis and all calyces with thinning of the renal parenchyma. The SFU classification system is used also in adults. 2 This classification system has good intra observer and interobserver reliability and is recommended for assessment of neonatal HN. 3 The most common reported causes of HN are kidney or ureteric calculi, pregnancy, pelviureteric junction (PUJ) stenosis or bladder outlet obstruction. 4 Ultrasound (US) imaging is commonly used, universally available, noninvasive and radiation free imaging modality. It is highly valuable in diagnosing and grading of HN. 5 This study was designed to investigate the efficacy of US in determining the cause of HN which is a common medical problem in all age groups and the detection of the cause of HN is a critical point for planning of the management. Moreover, the study was carried out to examine the causes of HN in adults and children due to lack of enough similar previous studies about causes of HN in adults and children which is a common and important topic and many previous studies were concentrated only on prenatal and neonatal HN. This work will be beneficial for ultrasonographists, radiologists, urologists and emergency practitioners who are usually interested in detecting the cause of HN as a frequent and important problem corresponds to their daily work.
This study also elucidate the distribution of HN in the right and left kidneys and in male and female gender and explained the cause of predilection of HN to right side in female.

METHODS
This cross-sectional retrospective study involved 233 patients who underwent abdominal US imaging and diagnosed with HN at the US unit of Amran hospital in Yemen during the period from 1 st January 2016 to 31 st October 2017. This study involved both adults and children. Exclusion criteria include prenatal HN because a lot of previous studies satisfy this topic. Procedure: All patients were scanned by the same radiologist who has eight years of experience in abdominal ultrasonography. A 3.5 MHz curved transducer of Medison, Sono ex-model six color Doppler machine was used in scanning of all patients. Each patient was scanned in supine and oblique positions to demonstrate and grading HN. Each kidney was examined in longitudinal and transverse sections with an examination of the whole ureter and urinary bladder to demonstrate the cause of HN.
Patients were scanned by the same highly experienced radiologist following the protocol of ultrasound imaging of the kidneys. Statistical Analysis: The collected data were analyzed using the statistical package for social sciences (SPSS), IMB, version 23 for windows (Armonk, NY: IBM Corp. 2015). Chisquare test was used to compare urinary calculi in gender and side. P value was assumed to be significant when < 0.05. Cross tabulation was used to analyze relationship between gender and side distribution of urinary calculi. Results were reported as frequencies and percentages in categorical data. Ethical Approval: Institutional ethical approval was obtained for this study. Confidentiality of the patients was assured during and after this study.

RESULTS
This study involved 233 patients who underwent abdominal US imaging and diagnosed as HN. 91.41% were adults and 8.58% were children, 66.10% were male and 33.90% were female. HN was unilateral in 88.85% and bilateral in 11.5%. HN was in the right kidney in 55.36% and 44.64% was in the left (Table-I).
Table-II shows that 58% of patients were suffering from mild (Grade-2) HN, 21.5% moderate (Grade-3), 11.6% minimal (Grade-1), and 8.2% severe (Grade-4) HN (Fig.1). Ultrasound imaging can determine the cause of HN in 70.4% of patients with HN. Kidney or ureteric calculi was the cause of HN in 54.1% of cases, 7.3% of cases were reflux HN, PUJ stenosis was the cause in 3.9%, and residual HN was determined in 1.7% of patients (Table-III). Regarding causes in children, calculi were the cause in 30% of cases, PUJ stenosis in 20%, reflux HN in 15%, residual in 5%, and 25% with no determined cause (Table-IV).
In cases of calculi induced HN, 25.3% of calculi were in the vesicoureteric junction (VUJ) or distal part of ureter, 21.5% were in the renal pelvis, 6.4% were in the PUJ or upper ureter, and only 0.9% were in the middle ureteric part (Table-V).
The cross-tabulation test between sex and side of HN shows predilection of HN to the right side only in female but not statistically significant (p=0.072), (Odds ratio= 0.832), (95% confidence interval (CI) 0.666-1.054), (Table-VI).

DISCUSSION
HN is a widespread health problem worldwide that can be present at any age because of multiple causes. Determining the cause of HN is an essential when planning the treatment.
In a previous study by Riddell et al., the sensitivity of bedside US imaging to detect unilateral HN was 72-83%. 6 In this study, we found that US imaging can determine the cause in 70.4% of all patients with HN. Another previous study by Moş et al. reported that transabdominal US imaging can identify HN in 88.94% and can identify ureteric calculi in nearly 73% of patients. 7 Sternberg et al. reported that HN on US imaging has a 77% positive predictive value for diagnosis of ureteric calcui with 71% negative predictive value. 8 In this study, we found that HN was more common in male than in female, mild (grade-2) HN was the most common and ureteric or kidney calculi were the most common cause even in children. These results were consistent with that of Nuraji and Hyseni., who reported that HN was more common in grade-2 and in males with kidney and ureteric stones were the most common cause. 4 These results are also consistent with a previous study by Abu-Ghazzeh and Abdu-Alro'f, who reported that calculi were the most common cause of obstructive HN and were most common in the VUJ. 9 Another similar study by Hansen et al. reported that calculi were the most common cause of HN in adults. He reported that renal pelvic, PUJ and VUJ calculi can be detected by US. However, calculi in the ureter are difficult to be detected due to obscuration by bowel gases. 10 This explains the low detection rate of ureteric calcui by US which reported in the results of this study. Calculi are the cause of HN in 54.1% of patients in the current study. This is consistent with another previous study by Alshoabi, who reported that calculi were the cause of HN in 60% of cases. 11 This study showed predilection of HN to male gender. This predilection was explained by the results of a previous study by Ahmed et al. who reported that urinary tract calculi, which are the most common cause of HN, are formed more common in males due to hormonal effects. 12 The high prevalence of nephrolithiasis in males is attributed to the effect of sex hormones such as androgens on some lithogenic risk factors which increases excretion and deposition of calcium oxalate in the pelvicalyceal system and kidney stone formation. In addition, estrogen decreases excretion of urinary oxalate and contribute in nephrolithiasis. 12 Sultan Abdulwadoud Alshoabi et al.