Laparoscopic retroperitoneal approach for urinary tract surgery. Predictive factors of complications and conversion to open surgery Cirugía urológica mediante acceso lumboscópico. Factores predictivos de complicaciones y conversión a cirugía abierta

Introduction: Surgery by lumboscopic approach is of choice for some work groups, despite being more arduous and requiring a higher learning curve. Objective: To assess the lumboscopic approach and identify predictive factors of complications and conversion to open surgery. Material and Methods: A transversal, retrospective study of 436 patients that underwent surgery by lumboscopy at the National Center for Minimally Invasive Surgery, 2008-2019. Absolute and relative frequencies; the Chi-Square Test and Student ́s t Test and the Multiple Logistics Regression, were utilized, (p≤0.05). Results: Renal atrophy due to benign diseases (49.8%), renoureteral lithiasis (26.6%), surgery of moderate complexity (71.9%) prevailed, such as nephrectomy (50.2%). 16.1% had undergone prior surgery, and 12.4% a urinary derivation. 3% required conversion to open surgery and 18.8% presented complications. Renal staghorn and non-staghorn lithiasis, surgical technique, level of complexity of the surgery, operative time, transoperative bleeding and length of hospital stay were significantly associated (p<0.05) to complications, but after measuring logistics regression, only hospital stay resulted statistically significant (p=0.000). Regarding conversion: gender, past history of prior surgery, operative time and bleeding were significantly associated (p<0.05) in both the univariate and multivariate analysis. Conclusions: Nephrectomy due to benign causes and surgeries of moderate complexity prevailed in this series. The perioperative outcomes were satisfactory and the most frequent complications were postoperative, infectious and of grade II severity. Longer hospital stay was a predictive factor for complications whereas males, past history of prior surgery, longer operative time and bleeding were identified as predictive factors for conversion to open surgery.


Introduction
The introduction of laparoscopic surgery in the field of Urology in the 90s of the 20th century, with its numerous advantages, has enabled the development of multiple surgical techniques. This via has been called direct retroperitoneal approach, lumboscopy or retroperitoneoscopy, without distinction. (2)(3)(4) This access has advantages: the anatomy is

Surgical Technique
The patient was placed in the lumbotomy po-

Ethical Considerations
The investigation was approved by the Institutional Review Board (IRB) and the Ethical Review Board (ERB) at the NCMIS. The ethical principles of the declaration of Helsinki for Medical Research with human beings were followed. Surgery of moderate complexity (71.8%) prevailed and in this group, the most frequent procedure was simple nephrectomy for benign diseases (50.2%). Resection of retroperitoneal cysts was a procedure of low complexity that was performed in 25.2% of the patients and 3% were procedures of high complexity. Table 2. were nephrectomies for renal lithiasis. 1.1% of these patients had prior renal percutaneous surgery.

Results
3.2% required reintervention, most by minimally invasive surgery. Only two patients (0.5%) that presented retroperitoneal abscess needed open surgery. Table 3. Two patients underwent percutaneous collection draining (grade IIIb) and 2.8% were reintervened under general anesthesia (IIIb). 0.5% was grade IV because they were admitted in the Intensive Care Unit (ICU). No mortality was reported (grade V). Table 4. and bleeding (p=0.000) were associated with significance and were taken into consideration in the multivariate analysis. Table 5.  In a previous study of this same work group regarding complications in lumboscopic simple nephrectomy, it was reported that 7.14% of the patients had a past history of more than one prior surgery, but no relation was found with the occurrence of more complications. (10,11) The presence of urinary derivation can add greater complexity to the lumboscopic approach. In the series, a percentage of patients, by no means insignificant, had some kind of derivation (nephrostomy or double J stent) inserted, which was related to performing nephrectomies, mainly or with lithiasis surgery (ureter lithotomy). In a study written by Galahwat et al. (12) the presence of nephrostomy was considered a predictive factor of complexity for lumboscopic surgery, because of adhesions and the difficulty this entails during the dissection of the perirenal space.   (3,6,8,14) Srivastava et al. (3) report an operative time of 141±26 min, similar to that of the series.
Liapis et al. (15) stated operative times of 30-400 min, whereas Rasweiller et al. (4) mentioned 30-360 min. Other authors report more blood loss, mainly related with the greater complexity of the surgical technique. (16) In an initial study of 200 cases, Rassweiler et al. (4)  In a multicenter study, Bachar et al. (19) reported that one third of the trans operative complications (5.2%) in nephrectomy due to benign diseases, were related with bleeding. Other authors also report that transoperative bleeding is more frequently associated with nephrectomy because of lithiasis and renal tumor, nephroureterectomy and tumorectomy; results that coincide with this study. (18,20) Infectious complications were the most frequent, fever without focalization prevailed which was treated with antibiotic therapy in 17 compared to other revised studies. (3,9,15) In this study, grade II complications prevailed, as in other investigations that report a prevalence of minor complications (grade I, II). (3,15,20) Al-Otaibi et al. (18)  complications. (9,19,21) Tepeler et al. (22) compared the rate of complications of lumboscopic nephrectomy between patients with renal lithiasis and other benign diseases and reported that it was higher in patients with lithiasis. Zelhof et al. (19) documented that nephrectomy for lithiasis is asso-ciated with a higher frequency of postoperative complications than nephrectomy due to other benign diseases. In 166 lumboscopic nephrectomies, González et al. (10) concluded that staghorn lithiasis is significantly associated with the occurrence of postoperative complications.
The level of complexity of the surgical technique is directly related to the incidence of complications. Fahlenkamp et al. (23)  organs can significantly complicate laparoscopic procedures and consequently, prolong operative time. (22,25) Patients with complications require prolonged hospitalization, which can explain the significant increase of the length of hospital stay with the occurrence of complications, but, at the same time, the longer the stay in a hospital institution, the higher the risk for complications. These outcomes coincide with those of other authors. (15,26)

Conclusions
Nephrectomy due to benign causes and surgery of moderate complexity prevailed in this series.
Perioperative outcomes were satisfactory and the most frequent complications were postoperative, infectious and of grade II severity.
Longer hospital stay was a predictive factor for complications while males, past history of prior surgery, longer operative time and bleeding were identified as predictive factors for conversion to open surgery.

Funding
No sponsorship was received to write this article.