Superior Mesenteric Artery Injury during Radical Nephrectomy in an Infant: Delayed Diagnosis and Successful Management.

Superior mesenteric artery (SMA) injury during a left radical nephrectomy is an uncommon complication in children with a potentially devastating outcome. Successful management depends on early diagnosis and re-establishing SMA perfusion. We report the successful management of an iatrogenic SMA injury during radical nephrectomy in a 10-month-old boy with left upper polar Wilms' tumor. Copyright:

INTRODUCTION

Injury to the superior mesenteric artery (SMA) is a rare and possibly an underreported complication during left radical nephrectomy. The consequences of an acute iatrogenic and unrecognized occlusion of the SMA can be disastrous for the patient. An untreated SMA occlusion with acute midgut ischemia is almost universally fatal.[12]

We report one such case of accidental SMA ligation during a left radical nephrectomy and its successful management.

CASE REPORT

A 10-month-old infant presented with a large palpable left Wilms' tumor.

The computed tomography (CT) scan revealed a large heterogeneous upper polar left renal mass with no vascular involvement. No hepatic, pulmonary metastases or significant lymph nodes were seen on imaging [Figure 1].

Figure 1

Preoperative computed tomography scan with large upper polar renal mass with mesenteric vessels close to the tumor

The tumor was approached transperitoneally, and the left renal vein was identified medial to the tumor. An artery appeared to be coursing parallel to the renal vein posterosuperiorly and entering the renal hilum. This was thought to be the renal artery. Following hilar control, the renal tumor was easily mobilized from the surrounding tissues. A second artery was found entering the renal hilum which was ligated, and the tumor was removed.

At this time, an intraoperative Doppler study confirmed good flow into the right renal artery. SMA injury was not suspected at this time because there seemed to be good expansile pulsation palpable in the root of the mesentery and the intestine appeared well perfused.

The patient developed an episode of hematochezia 6–8 h after surgery and a second episode soon after. The hemodynamic parameters were stable, and there were no signs of abdominal distension or peritonism. A bedside ultrasound of the abdomen 11 h after surgery reported poor flow in the SMA with mucosal edema of the terminal ileum. An urgent CT angiogram showed an abrupt cutoff at the origin of the SMA with retrograde contrast enhancement of the distal artery [Figure 2].

Figure 2

Postoperative computed tomography angiogram showing superior mesenteric artery discontinuity (arrow) with retrograde opacification of the distal stump

At immediate re-exploration (~12 h after the 1st), the bowel was pale and edematous with poor mesenteric perfusion. There was no pulsation in the mesenteric arteries, but the veins in the mesentery appeared free of thrombi and were filling in the prograde direction. The SMA was found ligated and divided flush with the aorta behind the pancreas proximal to the middle colic artery takeoff. The inferior pancreaticoduodenal artery was not separately visualized.

The ligature on the distal SMA was released, mobilized, and flushed with cold, heparinized Ringer's lactate solution. There was a free flow of the solution with no back bleeding. The proximal stump was too short for re-anastomosis. The left renal artery stump was of a similar caliber and long enough to be rotated without tension to be anastomosed to the SMA [Figure 3].

Figure 3

Schematic diagram showing anatomy at re-exploration and reconstruction using renal artery stump

The anastomosis was completed with 6-O polypropylene interrupted sutures. The bowel perfusion improved to normal immediately on releasing the clamps with good flow in the SMA.

The postoperative recovery was uneventful. The postoperative Doppler study of the superior mesenteric vessels before discharge revealed normal SMA flow [Figure 4]. The patient was discharged on full oral feeds on postoperative day 7. He is on regular follow-up for 18 months now having completed adjuvant chemotherapy with no intestinal sequelae.

Figure 4

Doppler study showing unobstructed flow in the superior mesenteric artery on postoperative day 7

DISCUSSION

Iatrogenic injury to the SMA during radical nephrectomy in children is rare and is also possibly underreported. Four cases of iatrogenic SMA injury during radical nephrectomy have been reported from the NWTS database.[3] These injuries are far more common during surgery for left-sided renal tumors.[12] Especially at risk are small children with large upper polar masses.[3] Injuries to the SMA have also been reported during surgery for large left adrenal masses in adults.[4] The mesenteric branches of the aorta can be displaced and stretched over the large mass making it difficult to differentiate from a similar sized renal artery during a difficult hilar dissection.[2] The presence of hilar adenopathy can add to the difficulty of the surgery increasing the risk of such injuries.[1]

When untreated, acute SMA occlusion is associated with significant mortality and morbidity.

The longest duration for which the bowel can safely tolerate SMA occlusion is unknown.[5] It has been suggested that the bowel can tolerate a 75% decrease in SMA perfusion in the presence of collaterals and a patent inferior mesenteric artery (IMA). Concurrent ligation of the SMA with the IMA or the superior mesenteric vein (SMV) is not tolerated well.[3] The early stages of acute SMA occlusion are characterized by features of bowel hyperactivity in the form of colics, vomiting, and hematochezia. The possibility of bowel salvage is most when reperfusion is achieved during this phase. Intervention in the subsequent stages, when bowel paralysis, devitalization with or without sepsis, and shock have set in, results in much poorer outcomes.[5]

Fullen et al. divided the SMA into four zones from proximal to distal. They proposed that zone 4 injuries at the level of segmental branches have little or no clinical significance. Zone 1 injuries proximal to the inferior pancreaticoduodenal branch of the SMA mandatorily require intervention. Collateral supply from the IMA may help preserve small bowel vascularity in some children even with proximal SMA injuries.[36]

The patient described in this report was at a high risk for iatrogenic SMA injury.

He had a large left upper polar mass displacing the root of the mesentery anteriorly. The tumor was deemed operable at initial assessment, and neoadjuvant chemotherapy was not given.

The bowel, even after the inadvertent ligation of the SMA, looked well perfused on inspection. An intraoperative ultrasound Doppler examination of the contralateral renal artery was done, but SMA evaluation at the same time was overlooked because an injury to the artery was not suspected.

The re-exploration and reperfusion of the intestine were performed approximately 12 h later, at which time, although the bowel was pale, there were no signs of congestion or thrombi in the smaller mesenteric vessels. The CT angiogram performed before re-exploration showed retrograde opacification of the SMA distal to the ligature. We surmise that collateral supply from the IMA through the middle colic artery was responsible and helped preserve critical bowel vascularity which allowed complete bowel salvage following the re-anastomosis. The patency of the SMV was an additional favorable factor in maintaining collateral circulation and preventing bowel congestion.

The poor reliability of gross appearance in assessing small bowel perfusion early after SMA injury has been stressed by various authors. Awareness of the risk factors for such an injury, having a high index of suspicion and use of intraoperative Doppler ultrasound examination can aid in early diagnosis of this potentially devastating complication of radical nephrectomy.[23]

Once diagnosis is made, re-establishing SMA continuity and perfusion is of utmost importance. In most cases, an end-to-end anastomosis of the divided ends suffices to restore bowel perfusion. Autologous vascular grafts, synthetic grafts, and direct reimplantation to the aorta have also been described as methods to repair the SMA.[123] Direct reimplantation into the aorta may be limited by inability to mobilize the distal SMA stump and thus resulting in a repair under tension.[3] The use of the renal artery stump to reconstruct the SMA resulted in a tension-free anastomosis with no luminal discrepancy. The delayed postoperative Doppler showed good flow in the SMA with normal resistive indices.

An extensive literature review did not yield a similar method of using the left renal artery stump to repair an iatrogenic SMA injury described before. This seems to be the only instance of such a repair described in English literature to the best of our knowledge.

CONCLUSION

The incidence of SMA injuries during left renal surgery may be underestimated.

The clinical appearance of the intestine following SMA injury may not help diagnosis, and hence, a high index of suspicion is necessary for early diagnosis.

Children reported to have tolerated SMA occlusion well and have done so presumably because of collateral circulation from the IMA.

The use of renal artery stump to establish a tension-free SMA repair has not been described to the best of our knowledge.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.