Early postoperative effects of ureterorenoscopy on morbidity and renal functions in ureteral stone patients with nondialysis-requiring renal insufficiency

Abstract

In this study, we aimed to investigate the effects of ureterorenoscopy (URS) on morbidity and renal functions in patients with ureteral stones and nondialysis-requiring renal insufficiency. The data of 3200 patients who had ureterorenoscopic lithotripsy and diagnostic URS were analyzed retrospectively. Age, urea and creatinine levels in the preoperative period and 4 h after surgery, the size of the stone, duration of surgery, percentage change in urea and creatinine levels [(last level−first level/first level) × 100] and postoperative complications were noted. Student’s t-test was used for the intergroup analysis of continuous variables. p < 0.05 was considered as statistically significant. There were 90 patients in nondialysis-requiring renal insufficiency group (group 1) and 101 patients in the control group (group 2). Percentage changes of urea and creatinine levels in the renal insufficiency and the control groups were found as −0.3% ± 3.3, 0.67% ± 3.9 and 2.3% ± 23.2, 2.5% ± 31.6 (p = 0.24 and p = 0.56), respectively. In group 1, three (3.3%) patients had postoperative febrile urinary infection, however febrile infections were not seen in any of the patients in group 2 (p = 0.06). Our results indicated that URS might be used safely in ureteral stones of the patients with nondialysis-requiring renal insufficiency.

• Complication
• renal insufficiency
• uremia
• ureteral stones
• ureterorenoscopy

Introduction

It has been supposed that presence of preoperative renal disease increases the risk of deterioration in postoperative renal functions. Since patients with severe renal insufficiency may be asymptomatic, analysis of preoperative renal functions is mandatory.1 In addition, all agents used in general anesthesia seem to decrease renal blood flow in proportion with the depth of anesthesia.2 Spinal anesthesia causes small changes in renal blood flow.3

Ureterorenoscopy (URS) is an endoscopic procedure frequently used in the diagnosis and treatment of renal and ureteral stones as well as the tumors of ureters. The diameters of today’s modern, standard, rigid ureterorenoscopes are usually smaller than 8 F, and they can be used easily for visualization of entire ureter.4 The most efficient and gold standard lithotripsy method used together with URS is Holmium YAG (Ho:YAG) laser, since all types of stones can be crushed effectively by this method.5^,6 The success rates of URS in distal, middle and proximal ureteral stones were reported as 93%, 87% and 82%, respectively.4

Although URS is used effectively and with low complication rates owing to increased experience of URS surgeons, technological advances in endoscopic equipment, and effective lithotripters, its safety has not been yet clearly determined in the ureteral stone treatment of patients with nondialysis-requiring renal insufficiency. In this study, we aimed to investigate the safety of URS on morbidity and renal functions in patients with ureteral stones and nondialysis-requiring renal insufficiency.

Material and methods

After obtaining approval of local Ethics Committee of our hospital, we retrospectively analyzed the data of 3200 patients who had ureterorenoscopic lithotripsy and diagnostic URS in our clinic between January 2003 and August 2014 with a prediagnosis of ureteral stone. A total of 90 patients who had chronic renal insufficiency and had had high urea and creatinine levels for more than 3 months, but did not need dialysis were included in study. The patients with a creatinine level >1.5 mg/dL who were consulted to Nephrology Clinic, and regarded to have renal insufficiency were included in the study. The patients with a solitary kidney and ureteral stone, the ones with acute renal failure and bilateral stones, and the ones end stage renal failure requiring dialysis were excluded. Successive 101 patients who had normal urea and creatinine levels and had URS were included in the study as the control group.

All the patients were operated after it was shown that they had sterile preoperative urine cultures. The height of the irrigation fluid above the kidney level was 65 cm in all patients. After the patients were given a lithotomy position, the ureter was entered using a single-channel 9.5 F ureterorenoscope (Karl Storz, Tuttlingen, Germany), with the help of a guidewire. After the stone was visualized, it was crushed using a pneumatic or holmium lithotripter. The stone pieces bigger than 1 mm in size were picked up with a basket catheter, smaller ones were let for a spontaneous passage. A double J (DJ) stent was inserted if needed, and when the surgeon considered it necessary. The stent was removed 2–4 weeks after the procedure.

Age, urea and creatinine levels in the preoperative period and in the first 12 h following surgery, the size of the stone, duration of surgery, percentage change in urea and creatinine levels [(last level−first level/first level) × 100], and postoperative complications such as fever, febrile urinary infection and macroscopic hematuria were noted.

The analysis of data was performed by using SPSS for Windows, version 11.5 (SPSS Inc., Chicago, IL). Normality of data distribution was analyzed with Shapiro–Wilk test. Descriptive statistics for variables with a normal distribution, and categorical variables were shown as mean ± standard deviation, and the number of cases and (%), respectively. Student’s t-test was used for the intergroup analysis of continuous variables. Paired samples t-test was used to determine whether pre- and postoperative urea and creatinine levels changed significantly. Categorical variables were analyzed with Chi square test. p < 0.05 was considered as statistically significant.

Results

A total of 191 patients who fulfilled the inclusion criteria, and had ureterolithotripsy or URS with the diagnosis of ureteral stone were included in the study. There were 90 patients in nondialysis-requiring renal insufficiency group (group 1) and 101 patients in the control group (group 2). The mean age of the patients in group 1 was 43 ± 14 years, and the mean age of the patients in group 2 was 42 ± 15 years (p = 0.56). There were 55 and 35 males in groups 1 and 2, respectively (p = 0.13). The mean stone size was 10 ± 4.2 mm in group 1, and 11 ± 3.5 mm in group 2 (p = 0.19). The mean durations of surgery were 29 ± 13.3 and 27.7 ± 11.2 min in groups 1 and 2, respectively (p = 0.49). The side and the localizations of the stones are presented in Table 1.

Table 1. Comparison of the side and localizations of the stones, and the complications between the groups.

	Group 1 (n = 90)	Group 2 (n = 101)	p
Laterality
Right ureter	53 (58.8%)	54 (53.4%)	0.45
Left ureter	37 (41.1%)	47 (46.5%)
Location (ureter)
Proximal	6 (6.6%)	9 (8.9%)	0.04
Middle	7 (7.7%)	22 (21.7%)
Distal	50 (55.5%)	45 (44.5%)
Diagnostic URS	27 (30%)	25
Macroscopic hematuria
Yes	6 (6.7%)	0	0.008*
No	84 (93.3%)	101 (100%)
Urinary tract infection
Yes	3 (3.3%)	0	0.064
No	87 (96.7%)	101 (100%)

Note: URS: Ureterorenoscopy.

*Statistically significant.

Percentage changes of urea and creatinine levels in the renal insufficiency and the control groups were found as −0.3% ± 3.3, 0.67% ± 3.9 and 2.3% ± 23.2, 2.5% ± 31.6 (p = 0.24 and p = 0.56), respectively (Table 2). The differences between the groups were not significant. There were no significant changes in postoperative urea and creatinine levels either in group 1 or group 2 when compared to preoperative levels (Table 3). Fifty seven (63.3%) patients in group 1 had surgery under general anesthesia while this number was 67 (66.3%) in group 2 (p = 0.66).

Table 2. Comparison of the groups for age, pre- and postoperative urea and creatinine levels, stone size, duration of surgery and percentage changes of urea and creatinine levels.

	Group 1 (n = 90)	Group 2 (n = 101)	p
Age (year)	43.8 ± 14.9	42.5 ± 15.3	0.55
Preoperative urea (mg/dL)	70.1 ± 13	33.7 ± 5.8	0.0001*
Preoperative creatinine (mg/dL)	3.8 ± 1	0.76 ± 0.15	0.0001*
Postoperative urea (mg/dL)	69.9 ± 13.1	33.7 ± 6.14	0.0001*
Postoperative creatinine (mg/dl)	3.8 ± 1.02	0.75 ± 0.16	0.0001*
Urea^a	−0.36% ± 3.3	2.3% ± 23.2	0.24
Creatinine^a	0.67% ± 3.9	2.5% ± 31.6	0.56
Stone size (mm)	1.09 ± 0.42	1.17 ± 0.35	0.19
Operation time (min)	29 ± 13.3	27.7 ± 11.2	0.49

Notes: ^aPercentage change.

*Statistically significant.

Table 3. Intragroup comparison of urea and creatinine levels between preoperative and postoperative early periods (paired samples t-test).

	Group 1 (n = 90)			Group 2 (n = 101)
	Preoperative	Postoperative	p	Preoperative	Postoperative	p
Urea (mg/dL)	70.1 ± 13	69.9 ± 13.1	0.27	33.7 ± 5.8	33.7 ± 6.14	0.96
Creatine (mg/dL)	3.8 ± 1	3.8 ± 1.02	0.23	0.76 ± 0.15	0.75 ± 0.16	0.57

In group 1, three (3.3%) patients had a postoperative febrile urinary infection, however febrile infections were not seen in any of the patients in group 2 (p = 0.06) (Table 1). Fever and infection were treated with culture-directed intravenous antibiotics. On the other hand, macroscopic hematuria was seen in six (6.7%) patients in group 1. A DJ stent had been placed in four of those patients. None of the cases with hematuria needed a blood transfusion. Four patients with hematuria were treated with antifibrinolytic treatment (transamine 2 × 1), and a bladder wash after inserting a 3-way Foley catheter, and two patients were treated by early removal of DJ stent. None of the patients in group 2 had macroscopic hematuria (p = 0.008).

Discussion

URS is a frequently used diagnostic and therapeutic intervention used in urolithiasis, treatment of ureteral strictures, biopsy and ablation of ureteral tumors, removal of foreign bodies from the ureters, evaluation of undiagnosed gross hematuria or ureteral filling defects and diagnostic evaluation of positive cytology in cystoscopy.7 Its success rates in distal, middle and proximal ureteral stones were reported as 93%, 87% and 82%, respectively.4 URS may be regarded as the first line treatment in painful ureteral stones unresponsive to expulsive treatment.

A mechanical cylindrical pumping device or manual injection syringe may be used during URS in addition to irrigation liquid in order to increase the quality of the image. However, use of those devices increases renal pelvic pressure. One study showed that renal pelvic pressure increased to 345–410 mmHg when an injection syringe was used.8 In a cadaveric study, Boccafoschi et al. showed that infrarenal reflux occurred below 30 mmHg in humans.9 It has been known that reflux increases the risk of infection, and it is directly related with infection. In addition, a relation was shown between the height of the irrigation fluid above the kidney level and intrapelvic pressure. Pyelolymphatic and pyelovenous back-flows were shown when the irrigation fluid bag was 50 cm above the renal level.10 On the other hand, Aldemir et al. studied the effects of URS on renal functions, and found that URS did not have any effect on renal functions other than an increase in 24-h urine protein.11 Similarly, in our study we did not find any significant changes in postoperative urea or creatinine levels of kidney insufficiency group (p = 0.27 and p = 0.23, respectively). In addition, the percentage changes in the urea and creatinine levels after surgery were similar in the renal insufficiency and the control groups (p = 0.24 and p = 0.56, respectively). In our study, the height of the irrigation fluid above the kidney level was 65 cm. We observed urinary infection in only three patients in the renal insufficiency group. There were no infections in the control group. The difference between the groups was not statistically significant (p = 0.06). Since aforementioned studies reported presence of pyelolymphatic and pyelovenous flows at the height of the irrigation fluid used in our study, this situation might explain presence of infection in patients with renal insufficiency that already had a low resistance to infection. On the other hand, the difference of the infection rates between the study and the control groups did not reach statistical significance.

It has been supposed that presence of preoperative renal disease increases the risk of deterioration in postoperative renal dysfunction. Uncontrolled local or systemic infections create predisposition for renal failure as a result of hypotension, disseminated intravascular coagulation and nephrotoxic antibiotics.12 Therefore, in our study we showed negative urine cultures in all the patients before URS, and then performed surgery. Serum creatininase levels reflect renal functions better than blood urea nitrogen since blood urea nitrogen levels are affected more by the volume status, urine output and protein intake.1 In our study, we tried to find whether we could safely perform lithotripsy in patients with ureteral stones in patients with non-dialysis requiring renal insufficiency. When the study and the control groups were compared for percentage changes of urea and creatinine levels, the changes were found similar in both groups, without any significant difference in between.

It has been known that most of the agents used in general anesthesia decrease renal blood flow in proportion with the depth of anesthesia, and affect renal functions negatively.2^,9^,13 However, spinal anesthesia causes small changes in renal blood flow and vascular resistance.3 Both general and local (spinal) anesthesia techniques were used in our study. Fifty-seven (63.3%) patients in group 1 had general anesthesia while this number was 67 (66.3%) in group 2. The anesthesia techniques used in two groups were similar (p = 0.66). In our study, we did not determine a negative effect of anesthesia on renal functions in patients with non-dialysis requiring renal insufficiency.

The complications of URS decreased in the past 20 years parallel to advances in ureteroscopes, contributory equipment, intracorporeal lithotripters and most importantly increased experience of the surgeons. The most frequently seen early complications include gross hematuria, renal colic, big residual pieces, pyelonephritis, urinoma and irritation symptoms due to the ureteral stent.7^,14–16 Macroscopic hematuria was seen in six (6.7%) patients with renal insufficiency (p = 0.008). None of the patients had bleeding requiring blood transfusion. Chronic renal failure patients have an increased tendency for bleeding due to uremia. The rate of hemostatic dysfunction is 40–60% in uremic patients. The reasons for it are platelet abnormalities, and dysfunction of plasma coagulation proteins accompanying platelet abnormalities. Platelet production is not disturbed in patients with chronic renal failure, however a platelet dysfunction is present. The coagulation factors are normal, but there is a dysfunction of thrombocyte factor III. The problem is due to abnormal interaction of platelets with the vessel wall. Although bleeding time is long in those patients, prothrombin and partial thromboplastin times are normal.17 Higher rate of macroscopic hematuria in our renal insufficiency group when compared to controls might be explained by the higher bleeding tendency is in those patients when compared to the normal population.

The present study investigated the effects of treatment of ureteral stones with URS on renal functions in patients with nondialysis-requiring renal insufficiency, and to our knowledge, this subject has been investigated in the literature for the first time. We included the patients with renal insufficiency (creatinine >1.5 mg/dL) not requiring dialysis in our study. Retrospective nature of our study is its limitation. However, relatively high number of patients was included, and the homogeneity of the study group constitutes the power of our study.

In conclusion, our study indicated that URS may be used safely for treatment of ureteral stones in patients with nondialysis-requiring renal insufficiency. However, increased tendency for bleeding and infection in those patients must be kept in mind. Further prospective randomized studies supported by experimental studies, with a longer follow-up period, and larger patient cohorts are needed to clearly describe the effects of URS on the kidneys.

Declaration of interest

The authors report no conflicts of interest.