Experience in identifying the variant adrenal venous anatomy during modified retroperitoneoscopic adrenalectomy.

BACKGROUND: Adrenal vein plays an important role in performing laparoscopic adrenalectomy successfully. However, it often presents with a multitude of venous anatomical variants. Hence, having a thorough knowledge on the variant types is crucial to reduce operative complications. This study aims to present our experience in identifying adrenal vein variation in adrenalectomy through modified retroperitoneal approach. PATIENTS AND METHODS: A total of 187 patients underwent modified retroperitoneoscopic adrenalectomy between July 2017 and February 2019. Perioperative data and adrenal vein variants were recorded and analysed.
RESULTS: Variant adrenal veins were encountered in seven patients. On the right side, two cases were drained by two adrenal veins; one case had a common trunk of adrenal vein and an accessory hepatic vein and one case had an adrenal vein joined with the opening of the right renal vein. On the left side, two cases of anatomic variations were described as follows: one vein converged with the left inferior phrenic vein and joined with the left renal vein, whereas the other vein directly joined with the left renal vein. One case had two adrenal veins that joined with the left renal vein.
CONCLUSIONS: Accurate identification and proper handling of the anatomical variation in the drainage of adrenal vein are crucial to safe LA. It is helpful to anticipate and avoid bleeding, especially in large adrenal tumours.

INTRODUCTION

Laparoscopic adrenalectomy (LA) is the procedure of choice for most adrenal tumours. An important request of LA is to identify and control the adrenal veins correctly. Not only that, a clearer understanding of the adrenal veins is necessary to adrenal venous sampling, which is the gold standard for aetiological diagnosis and distinguishing unilateral from bilateral disease.[1] Therefore, urologists and radiologists should have a thorough knowledge on the types and frequency of adrenal vein variations to perform successful surgeries.

Venous drainage from each adrenal gland, described in the standard anatomical textbooks, is usually through a single vein: the right side joins the inferior vein cava and the left one joins the inferior phrenic vein and then drains into the left renal vein. The anatomical variation of adrenal veins is relatively rare and easily be overlooked. However, these variations increase the risk and difficulty in performing LA, particularly in patients with larger adrenal tumour because the large size of the tumour often predisposes to increased risks of adrenal vascular variation. During LA, early identification and ligation of the main adrenal vein is a crucial step. It requires the surgeon to skilfully distinguish and anticipate the adrenal veins, especially avoiding omission of and causing injury to the variant adrenal vein. So far, only few clinical reports have been published on adrenal vein variation, of which majority of the published reports and conclusions are based on LA which were performed through transperitoneal approach. Besides, other related reports have been mainly described in cadaver studies.[23] They reported different pathophysiologic features because the cadaver studies were carried out on non-diseased adrenal glands. It is difficult to infer the variability of venous drainage in adrenal tumour cases only through cadaver studies. The purpose of this study was to introduce the importance and experience in identifying variant adrenal vein anatomy during LA through retroperitoneal approach.

PATIENTS AND METHODS

Patients

From July 2017 to February 2019, a total of 187 patients underwent retroperitoneoscopic adrenalectomy and had been studied retrospectively. All patients underwent contrast-enhanced computed tomography (CT) scan. Pre-operative data included patient characteristics, tumour size and endocrine diagnosis, including aldosterone, renin activity, plasma cortisol, plasma ACTH, 24-h urinary cortisol, catecholamines, metanephrine and normetanephrine. Serum electrolyte levels were also evaluated. The entire pre-operative preparation followed the classical principle reported in the previous publications or the latest guidelines.[4] Intraoperative information included the details on the main venous drainage, any variant veins and bleeding complications. Adrenal variations, in this work, were found incidentally during the operation rather than on pre-operative CT. The post-operative information included further requirement for intervention and recovery situation.

Surgical procedures

We removed the adrenal tumour through a retroperitoneal laparoscopic approach. The patients were placed in a full lateral decubitus position with overexpression under general anaesthesia. Initially, a 2-cm skin incision below the 12th rib in the posterior axillary line was made, the peritoneum was pushed forwards by the index finger so as to create the retroperitoneal working space and then a 12-mm trocar was inserted. A 10-mm trocar was placed above the iliac crest in the mid-axillary line for laparoscopy. A 5-mm trocar was placed 3–5 cm in the ventral aspect of the second trocar as a modified incision. The surgical procedures were identical to those of previous publications (omitted).[56] The adrenal tumour must be carefully isolated and lifted so as to seek for possible anatomical variation when handling the adrenal vein. Finally, the adrenal specimen was placed in a specimen bag and retrieved through the dissected incision linking a 5-mm and a 10-mm ports. The operation time was defined as the time elapsed between skin incision and skin closure.

RESULTS

All operations were performed successfully without conversion to open surgery. The mean operation time was 51 min (range: 39–73). The mean estimated blood loss was 24 ml (range: 16–120). Oral intake was resumed for 1.5 days (range: 1–3) after surgery. The drainage tube was removed after 1.6 days (range: 1–4). The average length of hospital stays was 7.1 days (range: 6–9). The characteristics of all patients are shown in Table 1. Of these 187 patients, seven (four males and three females; four on the right side and three on the left side) were found with adrenal vein variation. The detailed diseases' category and demographics of all the seven patients are listed in Table 2.

Table 1

All patients undergoing modified retroperitoneoscopic adrenalectomy

Variable	Value
Number of patients	187
Sex (n)
Male	89
Female	98
Age (years)	43.8±11.4
Side (n)
Right	94
Left	90
Bilateral	3
Pathologic diagnosis (n)
Cortisol adenoma	11
Non-functional adrenal tumour	14
Adrenal hyperplasia	59
Aldosterone adenoma	94
Pheochromocytoma	9
Duration of operation time (min)	51±7.5
Mean estimated blood loss (ml)	24±3.8
Oral intake (day)	1.5±0.4
Drainage tube removing time (day)	1.6±0.9
Hospital stay (day)	7.1±2.2

Table 2

Variant adrenal venous and pathologic diagnosis of seven patients

Patients	Side	Pathology	Size (mm)	Type of variation
1	Left	NFA	42	Two adrenal veins that joined with the left renal vein
2	Right	APA	21	Adrenal vein joined with the opening of the right renal vein
3	Right	Pheo	56	Adrenal vein was drained by two central adrenal veins into the IVC
4	Left	Pheo	68	One vein converged with the left inferior phrenic vein and joined with the left renal vein, whereas the other vein directly joined with the left renal vein
5	Right	CPA	27	Common trunk of the adrenal vein and accessory hepatic vein
6	Right	APA	24	Adrenal was drained by two adrenal central veins into the IVC
7	Left	Pheo	63	One vein converged with the left inferior phrenic vein and joined with the left renal vein, whereas the other vein directly joined with the left renal vein

NFA: Non-functional adenoma, APA: Aldosterone-producing adenoma, Pheo: Pheochromocytoma, CPA: Cortisol-producing adenoma, IVC: Inferior vena cava

Of the seven variant patients, three cases were diagnosed with pheochromocytoma, one case with non-functional adrenal tumour, one case with cortisol adenoma and two cases with aldosterone adenoma by the post-operative pathologic results. Among them, patients with cortisol and aldosterone adenoma had smaller tumour size; other patients had larger tumour size (>4 cm). Patients with large-sized tumour or pheochromocytoma most often had higher variation rate than those with small-sized tumour [Table 2].

As far as right adrenal vein anatomic variation was concerned, two cases were drained by two adrenal veins; one case had a common trunk of adrenal vein and an accessory hepatic vein, whereas in the other case, the adrenal vein joined with the opening of the right renal vein. On the left, two cases of anatomic variation were described as follows: one vein converged with the left inferior phrenic vein and joined with the left renal vein, whereas the other vein directly joined with the left renal vein [Figure 1]. One case had two adrenal veins that joined with the left renal vein.

Figure 1

Variant adrenal venous anatomy: one vein converged with the left inferior phrenic vein and joined with the left renal vein, whereas the other vein directly joined with the left renal vein

During laparoscopy, the variant adrenal veins were carefully freed and clipped with Hem-o-Lock. None of the patients required blood transfusion. Two patients had bleeding complications without conversion to open procedure: one of them was haemorrhage because of invasion to the liver, whereas the other one was haemorrhage owing to accidental injury of hepatic short vein which was hidden behind the adrenal vein. No major post-operative complications occurred.

DISCUSSION

LA has become a gold standard treatment for adrenal surgery.[78] However, not all adrenalectomy cases can be corrected easily because of the depth of the adrenal vein and its narrow connection with major vessels. In clinical practice, many surgeons often attribute bleeding to crude manipulation. They seldom consider the possibility of omitting and injuring the variant adrenal vein. Laparoscopy allows a clear and magnified view of the adrenal gland and its surrounding structures, compared with that of open surgery or cadaver studies. With advances in laparoscopic procedures, surgeons have not much difficulty in identifying normal adrenal gland and vein. Instead, the emphasis and difficulty is on how to recognise and handle the variant adrenal veins correctly.

Usually, majority of the adrenal veins have constant venous drainage. It is through a single vein draining into the inferior vena cava on the right side, joining with the inferior phrenic vein and then draining into the left renal vein on the left side. At present, the anatomical variations of the adrenal blood vessels are reported rarely. Sèbe et al. showed some adrenal venous variation types.[9] Earlier reports have been documented in cadaver studies. However, these series were focused on venous drainage in normal adrenal gland. There was no adrenal gland pathology.[1011] In addition, it was difficult to confirm whether the adrenal tissue or veins are intact before the autopsy. Until now, comprehensive studies have been reported by Parnaby et al. and Scholten et al. through a transperitoneal laparoendoscopic approach.[1213] On the contrary, documentation has rarely been made on retroperitoneoscopic adrenalectomy. We performed an analysis on cases involving retroperitoneal approach so as to demonstrate the possible differences in identifying adrenal venous variation. Because different approaches yielded different surgical views and anatomic points, it might influence the findings of adrenal venous variation.

In this article, our series included seven patients with adrenal venous variation, and all patients successfully underwent retroperitoneoscopic adrenalectomy. Two patients had bleeding complications without conversion to open procedures: one of them was haemorrhage because of invasion to the liver, and the subsequent pathologic diagnosis was a large malignant pheochromocytoma (6 cm). The other one was haemorrhage owing to accidental injury of the hepatic short vein which was hidden behind the adrenal vein. In fact, creating awareness of multivessels and ways to controlling them is the critical step in adrenalectomy although the majority of bleeding complications can be handled by ultrasonic scalpel or dipolar coagulation. During surgery, it is usually easy to identify the first obvious adrenal vein because of its wide diameter and distinct position. However, in most cases, the second/other adrenal veins are found accidentally when we decide to create space for occluding the first adrenal vein with Hem-o-Lock. It requires careful separation of the adrenal vein to the maximum extent possible; for instance, dividing into the upper inferior phrenic vein, the lower renal vein and the inner inferior vena cava. Surgeons should pay more attention to this situation, especially during continuous bleeding after electrocoagulation. In addition, it is very crucial to create more operative space for adrenalectomy because spacious vision can clearly identify anatomical relations and blood vessel variations. In contrast, it may cause injury or omission if the separation of adrenal periadrenal vessels is performed in a narrow space.

In our study, larger tumours had more variant rate than that of smaller tumours. This would have caused by their biological character; for example, more invasion and the ability of vascularisation. In general, different medical institutions and surgeons have different surgical practices. In our country, most surgeons prefer to perform LA through retroperitoneal approach. Although it could not provide a more capacious space and clear anatomic landmarks when compared to transperitoneal approach, retroperitoneal laparoscopy provides direct exposure to the adrenal gland without the limitation caused by the liver and spleen. Many urologists are familiar with the retroperitoneal anatomy. Besides, in retroperitoneal approach, there is little stimulation of the peritoneum and carbon dioxide absorption compared with that of transperitoneal approach.[14] To our knowledge, only few reports are available on operating variant adrenal veins through retroperitoneal approach. We believe that retroperitoneal laparoscopy has an advantage in showing dorsal adrenal venous variation because of the lateral position. On the right side, the vena cava and the renal pedicle are the landmarks. The adrenal vein is found along the vena cava. On the left side, the adrenal vein is found above the renal vein. In addition, the possible variant veins could be easily exposed by isolating the planes between the upper kidney and the lower adrenal vein because the periadrenal fat/tissue from the diaphragmatic muscle plays an innate traction role in facilitating the subsequent separation. All these retroperitoneal features are helpful in finding out and handling adrenal veins. It could be an alternative choice for surgeons who are familiar with transperitoneal approach.

CONCLUSIONS

We successfully performed retroperitoneal LA for patients with adrenal venous variation. The patients recovered without any post-operative complications. As far as adrenal surgery is concerned, the key point is to handle the adrenal vein properly. Thus, it is necessary to know the normal and variant adrenal venous situations so as to better control blood vessels, thereby reducing the risk of bleeding.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.