Splenogonadal Fusion

28.1Introduction

•Splenogonadal fusion is a rare congenital malformation that results from an abnormal fusion between the primitive spleen and gonad.

•Splenogonadal fusion is a rare, benign, congenital anomaly thought to occur between the fifth and eighth weeks of intrauterine life where immature splenic tissue adheres to the developing gonad, epididymis or vas deferens. The splenic tissue is subsequently pulled in a caudal direction with descent of the gonad.

•It was first described in 1883 by Bostroem.

•Since then more than 200 cases of splenogonadal fusion have been described in the literature, most of them are single case reports.

•Its first categorization was made in 1956 by Putschar and Manion.

•Karaman and Gonzales in 1996 reviewed 137 cases of splenogonadal fusion and surprisingly 37 % of the patients had orchiectomy because of suspicion of a testicular tumor.

•This is of great importance and to obviate this physicians caring for these patients should be aware of this and intra-operatively if there is doubt concerning the nature of the swelling, intra-operative frozen section biopsy should be performed to avoid unnecessary orchiectomy.

•Splenogonadal fusion occurs more commonly in males with a male-to-female ratio of 15:1. This figure may of course be inaccurate due to the relative inaccessibility of the ovary to clinical examination.

•It is seen nearly always on the left side.

•Splenogonadal fusion typically presents as an asymptomatic testicular mass.

•Other manifestations may include acute testicular pain and swelling caused by ectopic splenic tissue infections.

•Splenogonadal fusion is a very rare congenital anomaly that must be kept in mind and thought of especially if a child presents with an unusual scrotal swelling.

•It is rarely diagnosed preoperatively.

•If suspected preoperatively, the diagnosis can be confirmed by a 99mTc-sulphur colloid scan.

•There are two types of splenogonadal fusion, continuous and discontinuous.

•In continuous splenogonadal fusion there remains a connection between the main spleen and gonad.

•In discontinuous splenogonadal fusion, ectopic splenic tissue is attached to the gonad, but there is no connection to the main spleen.

•The continuous form occurs when the normally located spleen is attached to the gonad by a discrete cord.

•In the discontinuous type the splenic tissue is attached to the gonad and completely separated from the normal spleen.

•Both types occur with equal frequency and the discontinuous type may be discovered incidentally during herniotomy or orchidopexy or present as a scrotal swelling. Awareness of this is of great importance to avoid unnecessary orchiectomy mistaken it for a testicular tumor (Fig. 28.1).

Fig. 28.1 A clinical intraoperative photograph of splenogonadal fusion diagnosed in a child with unusual testicular swelling

•Treatment is surgical excision and every attempt should be made to preserve the gonad at the time of dissection and excision which should not be difficult since true fusion with the gonad is rare.

•Although there have been few reports of an association of testicular neoplasms with splenogonadal fusion, it appears that this is a coincidental finding rather than an association as these tumors occurred in adults with undescended testes.

•The diagnosis of splenogonadal fusion should always be kept in mind and included in the differential diagnosis of testicular swelling in infants and children (Fig. 28.1).

28.2Etiology

•The exact etiology of splenogonadal fusion is not known.

•Embryologically, the testis starts to descend from its initial embryological position between the dorsal mesogastrium and the mesonephros at around the eighth week of intrauterine life.

•This occurs at the time of splenic development.

•Embryologically, the spleen is formed by a proliferation of mesodermal cells in the dorsal mesogastrium around the fifth and sixth weeks of gestation.

•As a result of normal gastric rotation, the spleen moves in front of the gonadal ridge and mesonephros.

•Splenogonadal fusion is thought to result from partial fusion of splenic and gonadal tissues in the fourth to eighth weeks of intra-uterine life.

•Subsequent descent of the gonad during the eighth to tenth weeks of gestation results in descent of a part of the developing spleen along with it.

•In the discontinuous type, there is complete detachment from the normal spleen while in the continuous type there is attachment to the normal spleen by a cord-like structure.

–This cord can be made up of splenic tissue or totally fibrotic.

–Occasionally, there are multiple nodules along this cord which represent foci of splenic tissue that got detached and developed separately. This however does not fully explain the occasional occurrence of right sided Splenogonadal fusion.

•It has been postulated that contact between the gonadal ridge and the primitive spleen precipitated by stress factors (vascular or otherwise) may be responsible for a continuous splenogonadal fusion.

•A more recent hypothesis is based on the capacity of splenic cells to migrate at early stages of development. The spleen is partly responsible for the development of blood cells in the fifth week of gestation. A migration and colonization of splenic cells to its nearby structures namely the gonadal anlage could be responsible for both splenogonadal fusion as well as the explanation for its high association to cryptorchidism.

•It is important to note that the splenic and the testicular tissue of splenogonadal fusion are normal hence orchiectomy or splenectomy is not indicated.

28.3Classification

•Putschar and Manion in 1956 and in a collective review of 30 cases classified splenogonadal fusion into two types, continuous and discontinuous.

•Splenogonadal fusion is divided into two types:

–Continuous

–Discontinuous

•In the continuous type, there is a direct connection between the normal spleen and gonad by a cord that may be:

–Totally made up of splenic tissue

–Multiple connected beads of splenic tissue

–A cord made up of fibrous tissue

•In the discontinuous type there is no connection between the normal spleen and ectopic spleen that is attached to the gonad. This is considered a rare variant of an accessory spleen.

•Both types occur with relatively equal frequency.

•Some authors have suggested that because of the high association of continuous splenogonadal fusion with limb defects, continuous fusion should be regarded as an independent syndrome classified by its associated defects (limb defects, facial or other structures).

•In cases of continuous splenogonadal fusion, 50 % are accompanied by other congenital malformations.

•The incidence rate of associated anomalies for continuous splenogonadal fusion is fivefold higher than that of discontinuous splenogonadal fusion and most cases are accompanied by limb defect syndrome. These are called splenogonadal fusion limb defect syndrome (SGFLD).

•The majority (83 %) of splenogonadal fusion limb defect syndrome (SGFLD) are seen in those with continuous splenogonadal fusion and 70 % are associated with micrognathia.

•Approximately one-fifth of continuous splenogonadal fusion patients also have other major congenital defects, such as limb hypoplasia, micrognathia, cardiac defects, palatal defects and anal defects.

28.4Associated Anomalies

•Splenogonadal fusion is associated to a wide variety of malformations.

•Cryptorchidism and inguinal hernias are the most common malformations associated with splenogonadal fusion.

•In total, 31 % of splenogonadal fusion patients are diagnosed with cryptorchidism or inguinal hernias, and in 59 % of cases the cryptorchidism is bilateral.

•Other malformations include:

–Limb defects such as peromelia

–Micrognathia

–Cleft palate

–Spinal malformations

–Cardiac anomalies

–Microgastria

–Osteogenesis imperfecta

–Spina bifida

–Congenital diaphragmatic hernia

–Anorectal anomalies

–Craniosynostosis

–Moebius syndrome

–Roberts’s syndrome which consists of limb deficiencies, facial anomalies due to premature centromere separation

•Splenogoadal fusion with limb defects has also been associated to the Hanhart anomaly and the femoral facial syndrome.

28.5Clinical Features

•Splenogonadal fusion is commonly asymptomatic discovered incidentally during routine herniotomy or orchidopexy.

•Many of these cases however go passed unnoticed or discovered at autopsy.

•In the pediatric age group, these patients commonly present with a scrotal swelling and may rarely present with an acute scrotal pain as a result of torsion or involvement of splenic tissue with other pathological conditions such as mumps, malaria, leukemia, trauma and infectious mononucleosis.

•The left side is far more commonly affected than the right in 98 % of the cases.

•It is more common in males with an M: F of 15:1. This however may not be true as the ovary is not easily accessible and since the majority of these cases are asymptomatic, the incidence of splenogonadal fusion in females may be underestimated.

•Not uncommonly splenogonadal fusion is associated with other anomalies or discovered during the evaluation of these associated anomalies. This is more so with the continuous type which is known to be associated with other associated anomalies in as much as 33 % of the cases.

•One of the most common forms of presentation of splenogonadal fusion is testicular swelling.

•This swelling might appear as a hydrocele if it is painless.

•The swelling may be accompanied by pain in cases where the ectopic splenic tissue is affected by systemic disease, like Malaria, or mumps.

•Splenogonadal fusion is commonly diagnosed in children and adolescents.

–The number of cases reported in patients <10 years of age account for 50 % of the total cases reported.

–The number of cases reported in patients <20 years old account for 70 %.

•Patients most commonly present under the age of 20 years with:

–Cryptorchidism

–Left inguinal hernia

–A left scrotal mass

•Splenogonadal fusion may be an incidental finding during an orchidopexy and in these patients it is important to recognize this and manage the patient accordingly.

•The presentation may, however, be due to the complications of the splenogonadal fusion including:

–Intestinal obstruction

–Acute painful scrotal splenic enlargement

–Rupture

•One-third of cases are associated with other congenital abnormalities including limb and orofacial malformation.

•These associated anomalies are more likely seen in the continuous form.

•There is also an association between splenogonadal fusion and testicular malignancy.

–In the literature, there are about seven reported cases of splenogonadal fusion and testicular malignancy but in all of these cases the malignancy developed in adults with undescended testes or following orchidopexy for undescended testes.

–This may represents an association rather than an increased risk in this subset group of patients as patients with undescended testes have a well-known increased risk of malignancy.

28.6Investigations

•Splenogonadal fusion remains a diagnostic challenge and rarely it is diagnosed preoperatively.

•The diagnosis of splenogonadal fusion should always be kept in mind and included in the differential diagnosis of testicular swelling in infants and children.

•Physicians caring for these patients should be aware of this and preoperative consideration of the diagnosis may help avoid unnecessary orchiectomy.

•The radiologic identification of splenogonadal fusion is important to prevent unnecessary orchiectomy due to its macroscopic resemblance to cancer.

•Imaging modalities including ultrasonography, computed tomography (CT), magnetic resonance imaging (MRI) and 99TCm spleen scanning, aid with the diagnosis of splenogonadal fusion.

•Recently, laparoscopy is used to diagnose and manage patients with suspected splenogonadal fusion.

•Scrotal ultrasound may show ectopic splenic tissue as an encapsulated homogeneous extra testicular mass, isoechoic with the normal testis.

•The presence of splenic tissue may be confirmed with a technetium-99m sulfur colloid scan.

•Often, the definitive diagnosis is made postoperatively by histology and orchiectomy is not necessary as the splenic tissue can be dissected off the testicle.

•The goal should be to preserve the testis and the use of frozen section may be useful in distinguishing between splenogonadal fusion and primary testicular and para-testicular neoplasms.

28.7Treatment

•Preoperative diagnosis of splenogonadal fusion is uncommon.

•Intraoperatively, the diagnosis may also be difficult and it not uncommon for this to be confused with a testicular tumor.