Laparoscopic resection of an exophytic, enhancing renal mass: A case report of left-sided splenorenal fusion

The presence of splenic tissue contained within Gerota’s fascia is a rare finding that may be related to a developmental anomaly or secondary to splenosis. Its presence may mimic primary renal neoplasms or a metastatic lesion [1]. We report a rare case of splenorenal fusion that presented as an incidental 1.5 cm enhancing mass arising off the upper pole of the left kidney.  A laparoscopic partial nephrectomy was planned; however, intra-operatively it was clear the mass was a separate entity contained within Gerota’s fascia. Final pathology revealed the presence of normal splenic tissue.

Congenital and acquired splenic abnormalities are frequently encountered, with the most common being a supernumerary spleen, observed in up to 30% of the population. An accessory spleen can be located anywhere within the abdomen and pelvis; over 70% are found in the left upper quadrant [2]. The presence of additional splenic tissue can be problematic in patients who require splenectomy for medical disease, including hereditary spherocytosis or idiopathic thrombotic purpura.  Despite a presumed curative splenectomy, patients with an unrecognized accessory spleen can develop disease recurrence.  Splenosis, ectopic auto-transplanted splenic tissue, frequently occurs after a splenic injury.   The incidence of splenosis varies by type of splenic insult and can develop in up to 20% of patients after splenectomy and in 67% of patients with splenic trauma [3].

Splenic fusion is a rare developmental anomaly of minimal clinical significance believed to derive from direct fusion of the spleen with retroperitoneal structures during development. Splenogonadal fusion is a frequently-described fusion anomaly having been reported over 150 times since its description over two hundred years ago [4].  This abnormality is associated with other developmental defects such as limb anomalies or facial defects [5].

There is debate whether splenosis of the renal fossa is a separate entity from splenorenal fusion.   No theories currently account for how splenic tissue after trauma or splenectomy would migrate through the perirenal fat and Gerota’s fascia.  In the absence of trauma or splenectomy, its presence is believed to represent a true splenorenal fusion likely resulting from splenic fusion to the metanephros during renal development [6].

We describe a rare case of left-sided splenorenal fusion that occurred in a young woman who underwent a left partial nephrectomy and was found with normal splenic tissue within Gerota’s fascia.

A 53-year old obese female with a past history of hypertension presented to the emergency room with acute chest pain. She had no prior surgical history and no previous trauma. An electrocardiogram confirmed the presence of atrial fibrillation.  A chest CT scan was performed to rule out a pulmonary embolism. Incidentally, the lower cuts of the scan demonstrated an enhancing left kidney mass. This exophytic 1.5 cm mass arose from the upper pole and extended posteriorly (Figure1).

After further staging, surgery was recommended and she opted for a laparoscopic partial nephrectomy.  Coumadin was held prior to surgery and she was bridged with heparin.

The patient was placed under general anesthesia and positioned in the left flank position.  Access and port placement with our technique have been described previously.[7] Sharp dissection was performed to reflect the colon and spleen medially. Upon entry into Gerota’s fascia, we noted an exophytic mass by the upper pole of the kidney. Blunt dissection carefully exposed the lesion and it soon became evident that the mass, while close to the renal capsule, was not in continuity. Once the mass was mobilized, the lower 5 mm trocar was replaced for a 10 mm trocar in order to extract the mass with a 10 mm EndoCatch bag.  After re-inspection for haemostasis, all port sites were closed and the skin edges re-approximated.

The patient was stable throughout the case and transferred to a non-monitored floor.  She was placed on clear liquid diet post-operatively and the foley catheter removed on the first morning. Her diet was advanced and she was discharged later on post-operative day 1.  On gross pathologic exam the mass was a 1.1 x 0.8 x 0.6 cm red oval-shaped nodule and consistent with normal splenic tissue on microscopic exam.

  Only roughly a half dozen cases of splenorenal fusion have been described in the literature, mostly associated with the left kidney.[1, 8-11] However, Rosenthal and colleagues reported a large right-sided case of splenorenal fusion [6].  The presentation of splenorenal fusion varies from symptoms of hypersplenism to incidentally-discovered masses.  Many of the previous reported cases resulted in a nephrectomy either for management of hypersplenism or for a suspicious renal mass. Fortunately our case was performed laparoscopically, with no unnecessary loss of renal parenchyma, and the patient required only an overnight hospital stay.

To avoid such a situation and a possible unnecessary radical or partial nephrectomy, correct preoperative identification of splenic tissue contained within Gerota’s fascia is required. As splenorenal fusion is a rare entity, it is likely that many clinicians would consider this in the differential and proceed with an operative intervention. However, in the setting of a prior splenectomy or trauma, there should be a moderate index of suspicion and it should be included in the differential of a very exophytic, enhancing left-sided renal mass.  Clinicians can also stumble on this diagnosis due to the increased utilization of biopsies for small renal masses. However if normal splenic tissue is identified without any renal neoplasm, it is also possible that the biopsy needle has tracked through the normal spleen. In this case it would be of utmost importance to discuss the likelihood of this scenario with the interventional radiologist.

The diagnosis requires special imaging, as splenic tissue cannot reliably be distinguished from renal cell carcinoma and other neoplasms with conventional studies such as ultrasound or CT[12]. To accurately image splenic tissue a 99m Tc-sulfur-colloid scan or 99m Tc–labeled, heat-damaged red blood cell scan can be performed.[10, 11, 13] MRI with ferumoxide contrast is a new imaging modality that can identify splenic tissue by enhancing cells of reticulo-endothelial origin [14]. If considered, a fine-needle aspiration or core biopsy may histologically confirm the diagnosis.  Those patients fortunate to avoid an unnecessary surgery should be watched and repeat imaging may be considered.

We report a left-sided exophytic, enhancing renal mass that was found after surgery to be a case of splenorenal fusion. Clinicians should be familiar with this rare occurrence, especially in patients with prior trauma or splenectomy. Various imaging modalities are available in addition to biopsy to confirm the diagnosis.

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