Splenogonadal Fusion

(1)

Pediatric Surgery, AlSadik Hospital, Qatif, Saudi Arabia

28.1 Introduction

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).

28.2 Etiology

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.