Splenogonadal fusion--a review of rare anomaly.
Splenogonadal fusion is a rare benign congenital malformation that is characterized by an abnormal connection between the spleen and the gonad or mesonephric derivatives. [1-4] It is also called as supernumerary intrascrotal ectopic spleen. 
The anomaly was first mentioned by pathologist Eugen Bostroem in 1883, but it was not until 1888 when pommer described the malformation in details.  In 1988, Petrik recruited and studied the largest series, consisting of 87 cases. Approximately 160 cases of splenogonadal fusion have been reported to date.  The most recent comprehensive review of splenogonadal fusion was in 1990 by Carrgher et al, describing 123 cases. [1-4]
Although splenogonadal fusion may occur in both sexes, it is much more common in males (in a 9:1 or 15:1 ratio according to various authors). Cases have been reported in intersexual also. It should be noted, that in 4 cases reported in females, splenic tissue was adjacent to ovary and mesovarium.  However, the embryological origin as described below does not explain the different incidence between both sexes, although cases in the ovary may be underdiagnosed because of the inaccessibility to the female gonads for examination and will probably never be diagnosed if they cause no symptoms and so have been found at autopsy or as incidental findings at laparotomy. [6,7]
Splenogonadal fusion may be diagnosed at any age (1-81 years), but is most often diagnosed in the first two decades of life (72% to 82%), with 50% of the cases diagnosed prior to 10 years of age. 
Most cases have occurred on the left side, but a single case of splenogonadal fusion occurring on the right side has been reported. 
Splenogonadal fusion is thought to occur between the 5th and 8th gestational weeks. The etiology of such anomaly is uncertain, but may be secondary to injury of the fetus during this time. The spleen appears as a thickening of the layers of splenic mesothelium of the dorsal mesentery of the stomach. The gonad, arising as an indifferent sex gland from the medial surface of the wolffian body, comes to lie in front of the primitive kidney on the posterior wall of the abdomen. Complex gastrointestinal rotation processes occur in the 5th and 8th week of development, resulting in a retroperitoneal position of duodenum and pancreas. This involves the fusion of adjacent celomic surfaces, during which the two organs are brought into close apposition, and fusion of the two is not inconceivable. Under such circumstances the gonad, in its descent during the latter weeks of intrauterine life, might readily drag along a tail of developing juxtagonadal splenic tissue. [1,5]
There is currently another theory stating that an abnormal development of the cranial suspensory ligament of testis causes an abnormal involution resulting in cryptorchism and colonization of the abnormal ligament by splenic cells. 
In splenogonadal fusion, splenic remnants are bound to the surface of the testis/ovary or epididymis where it is separated from the gonadal tissue by a capsule. However, it can be even in an intragonadal location. 
Only the few cases with intragonadal spleen would hardly be explained by the previous theory. Such cases may be hypothesized to occur as a consequence of induction of hemopoetic potencies in gonadal mesenchyma. 
Putschar and Manion classified splenogonadal fusion into two types which occur with the same frequency;
(1) Continuous type--the spleen and splenic remnants adhered to the testis/ovary, epididymis, or deferent duct are attached through a cord like structure which may be fibrous, totally splenic or beaded with multiple splenic nodule which is usually in a retroperitoneal location, but may sometimes be intraperitoneal. All the cases described in female patients are the continuous type. [10,11]
(2) Discontinuous type--no connection is found between both structures. It may be due to breakdown of the attachment cord or represent a rare variant of an accessory spleen.
Sneath proposed that inflammation over two opposing peritoneal surfaces namely, the gonadal ridge and spleen, could cause fusion. During gonadal migration, the peritonealized adhesion would lengthen and develop as a cord continuous with the spleen or rupture during development, making it discontinuous with the spleen. 
Association with Other Congenital Abnormality
Splenogonadal fusion may be associated with other congenital anomalies such as testicular maldescent and cryptorchism, inguinoscortal hernia (due to the inguinal closure defect produced by the fibrous cord), peromelia, micrognathia, hypoglossia, palatine defects, polymicrogyria, craniosynostosis, spina bifida, cardiac defects, diaphragmatic hernia, hypoplastic lung and anorectal abnormalities, abnormal fissures of lung and liver, hypospadias.  These have been reported in 30% of continuous forms. [13-19]
Association between splenogonadal fusion with limb abnormalities and micrognathia is common due to close proximity between differentiating precursor structures of shoulder bones, Meckel's cartilage and developing spleen. It is listed as a rare disease by the office of rare diseases (ORD) of the National Institutes of Health (NIH). This condition affects less than 2, 00,000 in the US population. Most patients die shortly after birth although some do survive into childhood. 
In 40% of cases, patients present with cryptorchidism, left inguinal hernia and a paratesticular mass, preferentially located close to the upper testicular pole. Occassionally, when the mass is intimately attached, differential diagnosis with paratesticular solid masses (rhabdomyosarcoma, lymphoma, metastasis etc) becomes very difficult. 
Although the presence of splenic remnants at scrotal level does not usually cause any problem, it should be reminded that the spleen, even when ectopic, may experience the same disorders as its normally located counterpart. This explains why in patients with hypersplenism and diseases where the spleen is involved, such as malaria, mumps, mononucleosis, or leukemia, splenic remnants adjacent to the testis may be affected similarly to the spleen, causing an enlargement of the mass associated to pain. Falmann and Settle reported cases of splenogonadal fusion presenting with painful scrotal swelling secondary to malaria. 
However, presentation may be due to the complications of the fusion, e.g. bowel obstruction, rupture.
Other presentations are infertility, testicular pain after gastroenteritis and acute scrotal pain resembling testicular torsion. 
Athough exceptional, germ tumors associated to splenogonadal fusion have been reported in three patients, all of them with a history of associated cryptorchism. 
Although preoperative diagnosis of this rare condition is difficult and rarely achievable, techniques of diagnostic imaging for confirmation are available for any suspected case of splenogonadal fusion.
The literature review revealed few cases where an ultrasound examination has been performed for splenogonadal fusion. No ultrasonographic differences exist between the accessory spleen and normal testis. A clearly outlined 2-3 cm mass in close paratesticular relationship is seen. Some authors advisees that when a mass with these characteristics is manipulated, it should be watched whether testicular movements translate into spleen movements, which would only occur when continuous fusion exists. 
However, Doppler ultrasonography may help to differentiate between splenogonadal fusion and paratesticular or testicular mass. The extensive vascularity observed by dopper ultrasonography of splenogonadal fusion is more extensive than any typical paratesticular or testicular tumor and may easily be compared to the vascularity of the patients own intraabdominal spleen. 
More recently, imaging using hifh frequency linear array probes with high color sensitivity showed different vascular patterns in focal testicular lesions, suggesting a "crisscross" pattern in primary malignancy which helps in further differentiation. 
Spleen Scintigraphy Enhanced by SPECT
Only two cases out of four previously reported cases where the diagnosis was suspected preoperatively, confirmation done by radionuclide scanning, using radionuclide sulfur colloid/Tc99m imaging to demonstrate splenic uptake by the mass.
Care should be taken to obtain good scintigraphic visualization of the spleen, the whole abdomen and pelvis. The sctroum should be scanned in case of scrotal mass. As the bridge of splenic tissue connecting the spleen and the left gondad may be thin or discontinuous, it is imperative to obtain scans of impeccable quality. The appropriate use of image processing may be required to enhance the low-count density of thin or small splenic tissue fragments.
The noninvasiveness, relatively low price, sensitivity and specificity make it well suited for screening purposes.
CT Guided Biopsy[3,4]
If diagnosis is suspected preoperatively, it is advised to take a tissue sample for confirmation, so that partial mass excision sparing the testis, particularly in young males, may be performed. Histologically, the mass consists of completely normal splenic tissue, including red pulp and sinusoids.
When the diagnosis is confirmed and no symptoms are present, it is controvertible whether further surgical intervention is needed. Surgical exploration is generally needed to rule out malignancy especially in patients with intratesticular mass. On surgical exploration, if a mass is highly suspicious of splenogonadal fusion by visualizing a 2-3 cm solid red mass consisting of a parenchyma similer to that of spleen, the splenic tissue can be severed from the tunica albuginea in order to prevent orchidectomy, but in some case, orchidectomy may be required when the splenic tissue is adherent to the testes making it difficult to separate. Frozen section is crucial if splenogonadal fusion is suspected in patient with single gonad. Given the fact that the majority (82%) of patients were younger than 30 years at the time of diagnosis, orchidectomy should be avoided as often as possible. Familiarity with splenogonadal fusion allows one to recognize the lesion intraoperatively and preserve the testis. [1-4]
There is a growing importance of laparoscopy in the diagnosis and treatment of splenogonadal fusion especially in the cases of intraabdominal cryptorchism. 
Splenogonadal fusion is a rare congenital abnormality that is rarely suspected preoperatively. Careful medical history recording and high suspicion for the condition with confirmation by sophisticated investigations may prevent the patient from unnecessary orchidectomy.
Received Date: 03.10.2012
Accepted Date: 03.10.2012
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Kaushal D Suthar (1), Bhavna N Mewada (2)
(1) AMC MET Medical College and LG Hospital, Ahmedabad, Gujarat
(2) Smt. NHL Municipal Medical College and Smt. SCL Hospital, Ahmedabad, Gujarat
Correspondence to: Kaushal D Suthar (email@example.com)
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|Author:||Suthar, Kaushal D.; Mewada, Bhavna N.|
|Publication:||International Journal of Medical Science and Public Health|
|Date:||Jan 1, 2013|
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