Splenogonadal fusion is a rare congenital malformation that results from an abnormal connection between the primitive

spleen The spleen is an organ found in almost all vertebrates. Similar in structure to a large lymph node, it acts primarily as a blood filter. The word spleen comes .

and gonad during gestation. A portion of the splenic tissue then descends with the gonad. Splenogonadal fusion has been classified into two types: continuous, where there remains a connection between the main spleen and gonad; and discontinuous, where ectopic splenic tissue is attached to the gonad, but there is no connection to the orthotopic spleen. Patients can also have an accessory spleen. Patients with continuous splenogonadal fusion frequently have additional congenital abnormalities including limb defects, micrognathia, skull anomalies,

Spina bifida Spina bifida (Latin for 'split spine'; SB) is a birth defect in which there is incomplete closing of the spine and the membranes around the spinal cord during early development in pregnancy. There are three main types: spina bifida occulta, men ...

, cardiac defects, anorectal abnormalities, and most commonly

cryptorchidism Cryptorchidism, also known as undescended testis, is the failure of one or both testes to descend into the scrotum. The word is from Greek () 'hidden' and () 'testicle'. It is the most common birth defect of the male genital tract. About 3% of ...

. Terminal limb defects have been documented in at least 25 cases which makes up a separate diagnosis of splenogonadal fusion limb defect (SGFLD) syndrome. The anomaly was first described in 1883 by Bostroem. Since then more than 150 cases of splenogonadal fusion have been documented, predominantly in males. The condition is considered benign. A few cases of testicular neoplasm have been reported in association with splenogonadal fusion. The reported cases have occurred in patients with a history of cryptorchidism, which is associated with an elevated risk of neoplasm. Splenogonadal fusion occurs with a male-to-female ratio of 16:1, and is seen nearly exclusively on the left side. The condition remains a diagnostic challenge, but preoperative consideration of the diagnosis and use of ultrasound may help avoid unnecessary

orchiectomy Orchiectomy (also named orchidectomy, and sometimes shortened as orchi or orchie) is a surgical procedure in which one or both testicles are removed. The surgery is performed as treatment for testicular cancer, as part of surgery for transgend ...

. The presence of splenic tissue may be confirmed with a

technetium-99m Technetium-99m (99mTc) is a metastable nuclear isomer of technetium-99 (itself an isotope of technetium), symbolized as 99mTc, that is used in tens of millions of medical diagnostic procedures annually, making it the most commonly used medical ra ...

sulfur colloid scan.

Classification

Splenogonadal fusion is separated into two types: *Continuous (55%): The native spleen is connected to the gonad. The connection occurs through a cord of splenic tissue or fibrous band. * Discontinuous (45%): Ectopic splenic tissue is present and attached to the gonad. An accessory spleen is present and the native spleen lacks the direct attachment to the gonad.

Pathogenesis

The cause of splenogonadal fusion is still unclear, and there are several proposed mechanisms. A developmental field defect that occurs during blastogenesis is the current explanation of pathogenesis. The

spleen The spleen is an organ found in almost all vertebrates. Similar in structure to a large lymph node, it acts primarily as a blood filter. The word spleen comes .

derives from mesenchymal tissue and an inappropriate fusion can happen between the gonadal ridge during gut rotation, which occurs between weeks 5 and 8 of fetal life. Splenogonadal fusion may result from an unknown teratogenic insult. The timing of this insult may correlate to the severity of associated defects. There is also postulation that fusion may occur due to adhesion after an inflammatory response or a lack of apoptosis between the structures. Siblings documented to have splenogonadal fusion and an accessory spleen provides additional evidence of a possible genetic component.

Associated Conditions

Additional congenital abnormalities are most often found associated with the continuous type of splenogonadal fusion. These abnormalities include

micrognathia Micrognathism is a condition where the jaw is undersized. It is also sometimes called mandibular hypoplasia. It is common in infants, but is usually self-corrected during growth, due to the jaws' increasing in size. It may be a cause of abnorm ...

macroglossia Macroglossia is the medical term for an unusually large tongue. Severe enlargement of the tongue can cause cosmetic and functional difficulties in speaking, eating, swallowing and sleeping. Macroglossia is uncommon, and usually occurs in children. ...

, anal atresia, and

pulmonary hypoplasia Pulmonary hypoplasia is incomplete development of the lungs, resulting in an abnormally low number or size of bronchopulmonary segments or alveoli. A congenital malformation, it most often occurs secondary to other fetal abnormalities that int ...

. The most commonly associated malformation is

. When limb abnormalities occur, Splenogonadal Fusion with Limb Defects is made as a separate diagnosis. Splenogonadal Fusion with Limb Defects is also of unknown cause but some literature suggests that the condition may be related to Hanhart syndrome and facial femoral syndrome. Splenogonadal fusion has also been identified in infants with

Möbius syndrome Möbius syndrome is a rare congenital neurological disorder which is characterized by facial paralysis and the inability to move the eyes from side to side. Most people with Möbius syndrome are born with complete facial paralysis and cannot clos ...

and

Poland syndrome Poland syndrome is a birth defect characterized by an underdeveloped chest muscle and short webbed fingers on one side of the body. There may also be short ribs, less fat, and breast and nipple abnormalities on the same side of the body. Typical ...

Diagnosis

Diagnosis can be challenging pre-operatively, as patients are commonly asymptomatic. Physical examination can aid in diagnosis if the mass is palpated, but further confirmatory tests are necessary. Females are reportedly less affected by splenogonadal fusion, though it is possible that the condition is underdiagnosed due to the difficulty of internal gonad examination in females. On scrotal

ultrasound Ultrasound is sound waves with frequencies higher than the upper audible limit of human hearing. Ultrasound is not different from "normal" (audible) sound in its physical properties, except that humans cannot hear it. This limit varies ...

, ectopic splenic tissue may appear as an encapsulated homogeneous extratesticular mass, isoechoic with the normal testis. Subtle hypoechoic nodules may be present in the mass. Limitations of

doppler ultrasonography Doppler ultrasonography is medical ultrasonography that employs the Doppler effect to perform imaging of the movement of tissues and body fluids (usually blood), and their relative velocity to the probe. By calculating the frequency shift of ...

include visualizing the nonspecific paratesticular masses which can mimic malignancies such as rhabdomyosarcoma or embryonal sarcoma.

Technetium-99m Technetium-99m (99mTc) is a metastable nuclear isomer of technetium-99 (itself an isotope of technetium), symbolized as 99mTc, that is used in tens of millions of medical diagnostic procedures annually, making it the most commonly used medical ra ...

sulfur colloid scan is sensitive to target the liver, spleen, and bone marrow, therefore the scans can be used to identify ectopic splenic tissue when clinical suspicion is high. When

sulfur colloid scans are not included in a patient's diagnostic workup, the diagnosis is often not made until the surgeon performs an abdominal exploration using

laparoscopy Laparoscopy () is an operation performed in the abdomen or pelvis using small incisions (usually 0.5–1.5 cm) with the aid of a camera. The laparoscope aids diagnosis or therapeutic interventions with a few small cuts in the abdomen.Medlin ...

which can visualize the splenic tissue grossly. Evaluation by

biopsy A biopsy is a medical test commonly performed by a surgeon, interventional radiologist, or an interventional cardiologist. The process involves extraction of sample cells or tissues for examination to determine the presence or extent of a dise ...

including

frozen section procedure The frozen section procedure is a pathological laboratory procedure to perform rapid microscopic analysis of a specimen. It is used most often in oncological surgery. The technical name for this procedure is cryosection. The microtome device that ...

is confirmatory for splenogonadal fusion.

Histological Histology, also known as microscopic anatomy or microanatomy, is the branch of biology which studies the microscopic anatomy of biological tissues. Histology is the microscopic counterpart to gross anatomy, which looks at larger structures vis ...

examination will show normal splenic tissue which is made up of red and white pulp. Many people with splenogonadal fusion go undiagnosed without complication during their lifetime. Many cases have been diagnosed at autopsy or incidentally after orchiectomy.

Treatment

Treatment remains controversial given the benign nature of splenogonadal fusion. Splenogonadal fusion does not have known clinical manifestations that require intervention. Clinical observation is considered when the mass is diagnosed pre-operatively. Surgery is often required to confirm the diagnosis and exclude a mimic of a malignant mass. Surgical approach should attempt to divide the mass and the gonad at the connecting plane for removal of the splenic tissue.

Orchiectomy Orchiectomy (also named orchidectomy, and sometimes shortened as orchi or orchie) is a surgical procedure in which one or both testicles are removed. The surgery is performed as treatment for testicular cancer, as part of surgery for transgend ...

is generally not indicated. Causality between splenogonadal fusion and future malignant transformation has not been established, but literature has highlighted infrequent cases of testicular neoplasms and splenogonadal fusion. These cases were found in patients who also had a history of

, which is a known risk factor for

testicular cancer Testicular cancer is cancer that develops in the testicles, a part of the male reproductive system. Symptoms may include a lump in the testicle, or swelling or pain in the scrotum. Treatment may result in infertility. Risk factors include an ...

References