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Introduction
The prevalence of urolithiasis is 7-10% and has increased over the past years1. There is a paucity or epidemiological reports in Mexico, but urolithiasis prevalence has been set around 3-4%. In Yucatan, it reaches up to 5.8% of population according to a report 20 years ago2.
Despite is a benign pathology, urolithiasis may cause progressive loss of renal function. This kidney injury is due to recurrent infections and urinary tract obstruction3. Patients with urolithiasis might develop renal exclusion. Simple nephrectomy is, therefore, indicated when renal exclusion is associated with recurrent urinary tract infections (UTIs) and/or chronic pain4.
Over the past decades, technological developments on minimally invasive surgery have displaced other approaches in nearly all urology procedures, including laparoscopic nephrectomy (LPN). Since Claymann in 1991 performed the first LPN, surgeons have adopted this approach and are to date the gold standard for nephrectomy3. The LPN is a challenging procedure, specially when facing fibrotic and inflammatory tissue. Nonetheless, LPN has proved some advantages over open surgery, such as; less postoperative pain, better cosmetic outcomes, and shorter recovery5-8.
They are limited number of studies reporting outcomes of LPN in patients with renal exclusion secondary to urolithiasis. In this study, we retrospectively evaluated the outcomes of LPN in patients with renal exclusion due to urolithiasis and aimed to understand which factors were associated with conversion to open surgery.
Methods
The records of patients with renal exclusion secondary to urolithiasis, who underwent simple LPN between 2016 and 2019 were retrospectively reviewed.
Demographic characteristics, medical history, surgical time, estimated blood loss, rate of conversion to open surgery, post-operative complications, hemoglobin drop, and creatinine, need for transfusion, and length of hospital stay were retrieved from all patients.
Categorical variables were analyzed using Chi-square and Fisher’s exact test. To evaluate the association between preoperatory, surgical findings, and the risk of conversion to open surgery. Statistical analyzes were conducted with the aid of SPSS Statistics v16.0.
All procedures were carried out by urology residents under supervision and by an expert attending urologist trained in laparoscopic surgery.
Results
Forty simple LPNs for renal exclusion due to urolithiasis were performed between 2016 and 2019.
Demographic characteristics
Simple LPN was performed in 17.5% (n = 7) patients due to chronic pain and in 82.5% (n = 33) due to UTIs. The right kidney was the most affected (55%, n = 22).
Mean age was 47 ± 10.8 and 82.5% were female. The mean BMI was 30.2 ± 5 kg/m2 and the 57.5% were obese. Moreover, 67.5% had Type 2 diabetes and 85% high blood pressure.
Preoperatory hemoglobin range was 11-13 g/dL, mean serum creatinine baseline was 0.95 mg/dL (Table 1).
Table 1 Demographic characteristics and pre-surgical test of patients
| Variables | % (n) |
|---|---|
| Age (y) 47.6 ± 10.9 | |
| Sex | |
| Male | 17.7 (7) |
| Female | 82.5 (33) |
| Lithiasis | |
| Renal | 35 (14) |
| Ureteral | 65 (26) |
| Side | |
| Left | 45 (18) |
| Right | 55 (22) |
| Indication for surgical procedure | |
| Chronic Pain | 17.5 (7) |
| Recurrent infection | 82.5 (33) |
| High Blood pressure | 67.5 (27) |
| Mellitus diabetes | 85 (34) |
| BMI (kg/m2) | 30.22 ± 5.19 |
| Serum Cr, baseline (mg/dL) | 0.95 (0.79-1.48) |
| Hb, baseline (g/dL) | 12 (11-13) |
BMI: body mass index; Cr: Creatinine; Hb: hemoglobin.
Surgical outcomes
Mean operative time was 165.2 ± 64. The mean operative estimated blood loss was 150 mL, (range 100-200 mL) in the cases that was not necessary conversion to open surgery. The cases were necessary conversion to open surgery, the mean operative blood loss was 650 ml (range 180-1625) (Table 2). Regarding renal hilum vascular anatomy, it was reported as abnormal in six cases (Table 3).
Table 2 Surgical outcomes
| Variable | Mean ± SD Median (percentile 25-75) |
|---|---|
| Serum Cr, baseline (mg/dL) | 0.95 (0.79-1.48) |
| Serum Cr, post-operative (mg/dL) | 0.94 (0.79-1.33) |
| Hb, baseline (g/dL) | 12 (11-13) |
| Hb, post-operative (g/dL) | 11 (9.25-12) |
| Hto, baseline (%) | 39 (36.2-40.7) |
| Hto, post-operative (%) | 34 (29.5-37) |
| Surgical time (min) | 165.2 ± 64.9 |
| Estimated blood loss (ml) | 150 (100-200) |
| Hto drop (%) | 4 (2-8) |
| Hb drop (g/dL) | 1 (1-2) |
Cr: Creatinine; Hb: Hemoglobin; Hto: Hematocrit.
Table 3 Characteristics of abnormal renal hilum anatomy
| Variable | % (n) |
|---|---|
| Hilar supernumerary renal artery originating from Renal Artery | 84 (5) |
| Supernumerary renal artery originating from abdominal aorta | 16 (1) |
Intraoperative complications included spleen laceration in two patients which were solved by simple laparoscopic coagulation.
Conversion into open surgery was necessary in 5 patients (12.5%), the main cause was vascular injuries and uncontrollable bleeding. Renal artery injury was reported in three patients, injury of inferior mesenteric vein was reported in one patient and one to the inferior cava vein.
Complications were classified following Clavien’s system as following: 10 (%) patients with grade ≤2 (nine blood transfusion and one post-operative fever) and one patient with Grade 4 (pulmonary embolism).
A comparison between LPN group to patients who required conversion to open surgery was conducted. Operative time was longer in those who underwent open conversion (152.6 ± 59.3) than those who solely underwent LPN (236.7 ± 49.7; p = 0.002). Abnormal vascular anatomy was associated with conversion (p = 0.001) (Table 4).
Table 4 Characteristics pure laparoscopic procedure versus converted
| Variable | Laparoscopic | Converted | p-value |
|---|---|---|---|
| BMI (kg/m2) | 30.20 ± 5.05 | 30.30 ± 6.44 | 0.967 |
| Serum Cr, baseline (mg/dL) | 0.98 (0.79-1.50) | 0.86 (0.76-1.97) | 0.726 |
| Serum Cr, post-operative (mg/dL) | 0.96 (0.79-1.33) | 0.82 (0.72-2.94) | 0.526 |
| Hb, post-operative (g/dL) | 11 (10-12) | 9 (7.7-11) | 0.041* |
| Hto, post-operative (%) | 34.5 (30-37) | 28 (25.7-32.5) | 0.021* |
| Surgical time (min) | 152.6 ± 59.3 | 236.7 ± 49.7 | 0.002* |
| Estimated blood loss (ml) | 150 (100-200) | 650 (180-1625) | 0.003* |
| Transfusion rate | 88.2 | 16.7 | < 0.001* |
| Hb drop (g/dL) | 1 (0.7-2) | 2 (1.7-3.7) | 0.041* |
| Abnormal vascular anatomy (%) | 5.9 | 66.7 | < 0.001 |
BMI: body mass index; Cr: creatinine; Hb: hemoglobin; Hto: hematocrit.
Surgical findings and conversion
Conversion was significantly associated with abnormal hilum vascular anatomy (p = 0.001), hilum adherences (p = 0.001), and hydronephrosis (p = 0.001).
Post-operative outcomes
The mean hospital stay was 3.55 ± 2.5 days (2-14). The patient that post-operative present pulmonary embolism was management in UCI for 8 days and 6 days in hospital stage. Pathologic assessment revealed chronic pyelonephritis in 92.5% (n = 37) and 5% (n = 3) xanthogranulomatous pyelonephritis.
Discussion
The relationship between urolithiasis and renal function impairment has been documented. Such damage to the kidney is secondary to recurrent UTIs or urinary tract obstruction3.
Overall, urinary stones are more common in men7; however, in our study, we observed a higher prevalence of nephrectomies in females but that does not have relationship with risk factor for conversion.
In South-east of Mexico, kidney stone was the leading indication about of 60% of nephrectomies8.
There are indications to perform simple LPN in patients with poor renal function, the most important are recurrent UTIs and chronic pain9.
In our study, recurrent UTI was the main cause for LPN, accounting for 82.5% of the cases, similar to other reports.
One of the most important studies was done by Zelhof and collages, reporting patients who underwent LPN for benign pathology, the group of patients that have concomitant urolithiasis had higher risk for conversion to open surgery10. Pareek and collages report a higher complications rate in the simple nephrectomy group (20 vs. 10.7) than in that of patients that underwent radical LPN11.
Factors such as xanthogranulomatous pyelonephritis, colon adherences, history of renal abscess, vascular injuries, and obesity have been identified as predisposing for conversion to open surgery12-17.
In our study, the surgical findings that were associated with conversion to open surgery were hydronephrosis and adherences involving renal hilum, whereas obesity and colon adherences were not associated.
Conversion rate open surgery reported by other authors was found around 1.6-9%8,16,17.
The conversion rate in our study was 12.5%. The most important factor to convert to open surgery was vascular injury.
The complications during procedures were secondary to spleen injury in two patients that were solved by simple coagulation and five vascular injuries that were the main reason to convert to open surgery, having global conversion rate of 12.5%, with no mortality.
The length hospital stay is lower than that reported in the literature. Cem Yucel et al., reported a hospital stay of 3.86 ± 1.4 days, and Angerri et al., reported 5.4 days. Our study found a hospital stay of 3.28 ± 1.58 days7,17.
This study acknowledge limitations, first, the retrospective nature, second, the relatively small sample of patients, and lastly, some outcomes were retrieved from surgical records as reported by surgeons.
Conclusion
Simple LPN is a safe technique for patients with renal exclusion secondary urolithiasis; however, it can be in some cases challenging due the presence of adherences and fibrosis, especially in patients with history of recurrent infections. The laparoscopic approach has many advantages as compared to open surgery. In our study, hydronephrosis, abnormal vascular anatomy, and hilum’s adhesions were the factors associated to open surgery conversion, although renal hilum abnormal vascular anatomy is an unclear factor, since renal hilum’s or adjacent fibrosis may bring difficulties in the proper identification of the vascular structures and the discrimination of a true vascular abnormality from a complex renal hilum. Therefore, prospective studies evaluating renal vascular anatomy are needs. Moreover, the conversion rate was low and the technique suggesting the technique is safe.
