Retroperitoneal Laparoscopy in Dogs: Access Technique, Working Space, and Surgical Anatomy

Learning curve for the laparoscopy-guided kidney biopsy procedure in small corpses of dogs and pigs

The use of renal biopsy through laparoscopy is increasingly present both in human and veterinary medicine. However, both techniques require skill and training to make the operator capable to do it. The learning curve allows the quantitative and qualitative assessment of the number of attempts and minimum time for the surgical procedure. The objective included establish the learning curve for laparoscopy-guided kidney biopsy procedures in dog and pig corpses. Six dogs and six pigs corpses weighing less than 10 kg were used for this study. All corpses underwent kidney biopsy performed through laparoscopy. Twenty-four operators, two per animal, performed 20 renal biopsies each (10 for each kidney), with 480 collection-procedures in total. Duration and difficulty of the procedure and the biopsy sample quality were evaluated and statistical analysis was performed using a mixed regression model with a random effect of individuals and multivariate analysis of data. There were 91.5% of the samples that were adequate for evaluation. There was no significant difference in the number of glomeruli or cortex percentage considering the attempts in either species, demonstrating the operator's ability since first collection. Swine samples showed higher amounts of renal cortex than canine samples. The procedure duration was shorter as more attempts were performed in dogs and pigs. From the fourth repetition, the professional reached a plateau for the variable related to 'collection', and from the second, the professional presented uniform duration for 'sample storage'. Operators of the swine model acquired more agility than the dog ones. The variable 'difficulty' decreased as more repetitions were performed, reaching a plateau in the sixth attempt. Seven renal biopsies laparoscopy-guided are required for an operator to be considered 'capable' to perform the procedure in the referred species included. The learning curve for image-guided kidney biopsy procedures improves the implementation of this technique and benefits patients that undergo this procedure.

Retroperitoneoscopy in the horse: Anatomical study of the retroperitoneal perirenal space and description of a surgical approach

BACKGROUND

Surgical approaches to the kidneys and perirenal structures are uncommonly performed in horses and several complications have been described with the current procedures.

OBJECTIVE

To describe the anatomy of the retroperitoneal perirenal space and investigate a retroperitoneal minimally invasive approach to access the kidney and perirenal structures in horses.

STUDY DESIGN

Descriptive, cadaveric study.

METHODS

Anatomical description of the retroperitoneal space was performed on three equine cadavers and the surgical approach was developed based on these dissections. Ten cadaveric horses underwent a retroperitoneoscopy. Five horses were placed in a right lateral recumbency position to explore the left retroperitoneal space and five horses were placed in a standing position to explore both left and right sides. Anatomical landmarks, working space and access to the renal hilus and perirenal structures were evaluated.

RESULTS

Dissections revealed that kidneys are surrounded by a renal fascia which delimits two spaces: a perirenal space between the kidney and the renal fascia, and a pararenal space between the renal fascia and psoas muscles or peritoneum. The retroperitoneoscopic portal was placed at the level of the dorsal aspect of the tuber coxae, 3 cm caudal to the last rib for the left side and 2 cm caudal to the last rib for the right side. Retroperitoneal access and working space were successfully established in all horses. The standing position allowed an easier dissection than lateral recumbency. Division of the perirenal fat allowed access to the kidney and adrenal glands as well as individualisation of renal vessels and ureter in the renal hilus.

MAIN LIMITATIONS

Study of cadavers precluded appreciation of haemorrhage or use the pulsating vessels as landmarks.

CONCLUSIONS

This study provides a description of the retroperitoneal perirenal space and describes a new surgical approach to access kidneys and perirenal structures in horses.

Cardiopulmonary changes induced by retroperitoneal insufflation in healthy dogs in sternal recumbency with the abdomen unsupported

This study assessed the effects of retroperitoneal carbon dioxide (CO₂) insufflation on cardiopulmonary variables and intra-abdominal pressure (IAP) in mechanically ventilated dogs in sternal recumbency with the abdomen unsupported, following placement of a positioning kit and towels under the pectoral and pelvic regions. General anesthesia was induced in eight healthy adult male Beagles. A Swan-Ganz catheter was placed in the pulmonary artery via the jugular vein for cardiac output measurements. A Foley urethral catheter was placed to monitor transvesical IAP. A 10 mm balloon blunt-tip trocar was inserted into the retroperitoneal space. With a fixed respiratory rate and tidal volume by mechanical ventilation, insufflation pressure was sequentially increased from 0 to 10 mmHg in 5 mmHg increments, followed by desufflation. All variables were measured before insufflation, 5 min after the establishment of each insufflation pressure, and after desufflation. At 10 mmHg, the IAP was nearly equal to insufflation pressure. Cardiopulmonary function was not compromised at any point, although the cardiac index (CI), heart rate, mean arterial pressure (MAP), and mean pulmonary arterial pressure increased within normal ranges. End-tidal CO₂ concentration, arterial CO₂ partial pressure, and oxygen delivery index (DO₂I) increased, whereas pH decreased, at 10 mmHg. CI, MAP, and DO₂I did not recover to baseline after decompression. Thus, retroperitoneal CO₂ insufflation up to 10 mmHg is well tolerated by mechanically ventilated dogs positioned in sternal recumbency with the abdomen unsupported, although sympathetic changes may occur with an insufflation pressure increase.

CT variants of the caudal vena cava in 121 small breed dogs

Computed tomography is increasingly used as a treatment planning method in canine patients with diseases of the retroperitoneum, however, published information on normal variations in the caudal vena cava (CVC) are currently lacking. The objectives of this retrospective descriptive study were to characterize CVC variants using CT angiography in a sample of small breed dogs and localize the CVC bifurcations for each variant. Inclusion criteria were small breed dogs (weight ≤ 15) that underwent contrast-enhanced CT scans of the CVC, abdominal aorta, and CVC tributaries. A total of 121 small breed dogs were sampled. Four right-sided and one left-sided CVC variations were identified: normal (88/121, 72.7%), caudal-partial split (17/121, 14.0%), partial duplication (8/121, 6.6%), complete duplication (7/121, 5.8%), and left-sidedness (1/121, 0.8%). The mean lumbar vertebral levels of the CVC bifurcation were L6.39 ± 0.41, L5.70 ± 0.35, L4.39 ± 0.42, L2.74 ± 0.38, and L6.4 in the normal, caudal-partial split, partial duplication, complete duplication, and left-sidedness types, respectively. The location of the CVC bifurcation, the relationship between the aortic trifurcation and the CVC bifurcation, and the location of the bilateral deep circumflex iliac veins with respect to the CVC bifurcation were significantly different among the right-sided types (P ≤ .001). Bilateral deep circumflex iliac veins joined to the ipsilateral common iliac veins and the CVC in the caudal-partial split and duplication types, respectively. The results of this study indicated that canine CVC variants may be frequent and should be considered during surgery or diagnostic imaging of the retroperitoneum.

Feasibility of single-port retroperitoneoscopic adrenalectomy in dogs

OBJECTIVE

To evaluate the feasibility of single-port retroperitoneoscopic adrenalectomy (SPRA) in dogs.

STUDY DESIGN

A pilot experimental study.

ANIMALS

Eight healthy beagle dogs.

METHODS

SPRA was performed on the left and right sides (4 dogs each). Resection of the adrenal gland was performed through a SILS port using a retroperitoneal approach. Operative time was defined from skin incision to the completion of skin suture. Postoperative pain was evaluated by using 3 pain scores. Integrity of the adrenal gland capsule was evaluated by histologic assessment.

RESULTS

Mean time taken to complete the SPRA was 44.1 minutes (range, 37-51) and was significantly longer on the right side than on the left side (P < .05). There were no complications intraoperatively or during 14 days of postoperative monitoring. The adrenal gland capsule was found to be injured in 3 of the 8 dogs by histologic assessment.

CONCLUSION

This is the first report of SPRA in the veterinary literature. With this technique it is possible to perform adrenalectomy with some risk of capsule penetration and with excellent visibility.

CLINICAL SIGNIFICANCE

This study suggests that SPRA is feasible and can be used to resect small adrenal tumors with minimal complications.