Congenital abnormalities

Early in embryonic life there is a common chamber the cloaca into which open the hind gut and the allantois. The cloaca becomes separated into the bladder and post-allantoic gut (rectum) by the down growth of a septum. About this rime an epiblastic bud, the proctodaeum, grows in towards the rectum. Normally fusion between these two structures occurs during the third month of intrauterine life.

Imperforate anus

(The term is used as a well-recognised description. Strictly it should be ‘agenesis’ and ‘atresia’ of the rectum and anus.) One infant in 4500 is born with an imperforate anus, or with imperfect fusion of the post-allantoic gut with the proctodaeum. The condition is divided into two main groups: the high and the low, depending on whether the termination of the bowel is above or below the pelvic floor. The low vari­eties are easy to diagnose and relatively simple to treat, and the outlook is good. The high varieties often have a fistula into the urinary tract together with a deficient pelvic floor, and are difficult to treat.

Low abnormalities (Fig. 61.12)

Covered anus. The underlying anal canal is covered by a bar of skin with a track running forwards to the perineal raphe. The track should be opened with scissors, followed by rou­tine dilatation of the anus.

Ectopic anus. The anus is situated anteriorly and may open in the perineum in boys, or more commonly in the vulva in girls, or rarely into the vagina. A plastic `cut back’ operation is required (Pena).

Stenosed anus. The anus is microscopic, but careful examination usually reveals a minute opening which responds to regular dilatation.

Membranous stenosis. Here the anus is normally sited, but is covered with a thin membrane which bulges with retained meconium. It is rare, and an incision will cure the condition.

High abnormalities (Fig. 61.13)

These are often associated with a fistulous connection between the blind rectal stump and the bladder, or other abnormalities of the pelvic structures.

Anorectal agnesis. A blind rectal pouch lies just above the pelvic floor its anterior aspect in the male is attached to the bladder and often there is a rectovesical fistula manifested by the passage of gas or meconium in the urine. In the female, the flstula is usually into the posterior fornix.

Rectal atresia. The anal canal is normal but ends blindly at the level of the pelvic floor. The bowel also ends blindly above the pelvic floor without a fistulous opening. This anomaly is rare but must be treated by mobilisation of the rectum and excision of the stricture. After that, end-to-end anastomosis of the anus and rectum must be attempted. More conservative measures are followed by an intractable stricture.

Cloaca. This occurs only in females and here the bowel, urinary and genital tracts all open into a common wide cavity. Commonly severe malformations of the area are associated with other developmental abnormalities, e.g. tracheobronchial fistula.

Clinical management

As congenital abnormalities are frequently multiple, very careful general examination of the baby must be made to exclude any other anomalies. It is urgent and important to determine whether the abnormality is high or low, and a radiograph will help.

Radiological examination

Six hours after birth sufficient air may have collected in the large intes­tine to cast an X-ray shadow. With a metal button or a coin strapped to the site of the anus, or a metal bougie inserted into the blind anal canal, the infant is held upside down for 3—4 minutes and radiographed in the inverted position (Fig. 61.14). The gas in the rectum will rise to the top and indicates the distance between the site of the metal indicator and the blind end of the rectum. If the distance is over 2.5 cm, the abnormality is ‘high’. This method, although useful, is sometimes vitiated by a plug of meconium in the rectum causing an apparent gap far in excess of that actually present. It may he necessary to wait until the baby is 24 hours old before rectal gas appears.

Where a ‘high’ lesion is suspected, an effort must be made to obtain a specimen of urine the presence of proteus or pyocynaneus usually signifies that a fistula is present. An intravenous (i.v.) urogram is recommended by some, even though there is a definite radiation risk. There may be gas in the bladder. A diagnostic perineal exploration is usually unwise it may prejudice the chances of further surgery.

Treatment

In the low abnormalities, this is usually simple and has been outlined when each condition was described above. The high abnormalities present a very difficult problem and each case must be considered on its merits. On the whole, newborn babies stand surgery very well, provided compatible blood is available, a clear airway is maintained postoperatively and inhalation of vomit prevented by nasogastric suction. The presence of other congenital abnormalities is also a most important factor to consider. The possibilities are:

   laparotomy, division of rectourethral flstula and transverse colostomy. A rectal ‘pull-through’ operation can be done later;

   laparotomy, division of fistula and ‘pull-through’ opera­tion in one stage; division of the flstula and rectal ‘pull-down’ operation through the perineum (this method is now rarely used);

  post-sagittal rectoplasty (PSARP) (Pena). Similar to above but via posterior approach;

  colostomy only (for the cloacal variety).

For the ‘pull-through’ operation the lower bowel is mobilised, and a new passage is created through the pelvic floor by passing a pair of curved forceps through it, keeping close to the urethra, to the site of the future anus. This is dilated by Hegar’s dilators so that the bowel can he pulled down and its mucosa stitched to the skin of the newly formed anus. (For details the reader is referred to the standard textbooks of operative surgery and the publications of Swenson, Duhamel and Nixon.)

In general, daily dilatation will be required for at least 3 months and it may be necessary for years.

In a high percentage of cases, imperforate anus is associated with other congenital abnormalities, especially of the urinary organs, and nearly half the deaths in cases of imperforate anus are due to other malformations.

Sacrococcygeal teratoma

Sacrococcygeal teratoma, although rare, is among the most common of the large tumours seen during the first 3 months of life. The frequency of the precoccygeal region for the development of a teratoma is explained by the fact that this area is the site of the ‘primitive knot’, a group of totipotent cells that retain their totipotentiality longer than any others save the sex anlage. Females are more often affected than males.

The tumour, which arises between the sacrum and the rectum, is firmly attached to the coccyx and, occasionally, to the last piece of the sacrum. At the time of birth some of these tumours are huge, and in 20 per cent of cases the infant is stillborn. The tumour tends to he large (Fig. 61.15), but it can be small enough to pass unnoticed until it enlarges or a complication ensues. It is this variety that is prone to become malignant, usually at about 10 months of age.

Treatment. Removal should be soon after birth; delay is liable to result in fatal ulceration, infection, rectal or urinary obstruction, or malignant change.

Operation: excision Cs undertaken through a longitudinal elliptical incision, the coccygeal attachment being left until the last. The coccyx must always be excised; occasionally the last piece of the sacrum must be removed also. There may be a fistula between the tumour and the rectum, but as a rule this is small, and can be closed safely without performing a colostomy. The dead space in the pelvis is drained, the skin united and a pressure dressing applied.

When the operation is undertaken soon after birth, the prognosis is good.

Postanal dermoid

The space in front of the lower part of the sacrum and coccyx is occupied by a soft, cystic swelling — a postanal dermoid cyst — which is regarded as a simple form of teratoma. Hidden in the hollow of the sacrum, it is unlikely to be discovered unless a sinus communicating with the exterior is present, or develops as a result of inflammation. Such a cyst usually remains symptomless until adult life, when it is prone to become infected. Exceptionally, by its very size, it gives rise to difficulty in defecation. The cyst is easily palpable on rectal examination.

Differential diagnosis. Especially in a child, an anterior sacral meningocele must be excluded. The latter enlarges when the child cries, and is frequently associated with paralysis of the lower limbs and incontinence. When a discharging sinus is present, a post anal dermoid will probably be mistaken for a pilonidal sinus, unless pressure over the sacrococcygeal region with a finger in the rectum causes a flow of sebaceous material, and injection of contrast and radiography reveals a bottle-necked cyst in front of the coccyx.

Treatment is complete excision of the cyst, and sinus if present. In the case of large cysts it is necessary to remove the coccyx in order to gain access.

Postanal dimple (syn. fovea coccygea)

A dimple, sometimes amounting to a short blind pit, in the skin beneath the tip of coccyx, is noticed from time to time in the course of a clinical examination.

Pilonidal sinus

Pilonidal means ‘appertaining to a nest of hair’ (Latin: pilus = hair, nidus = nest).

  A etiology

The army of supporters of the congenital theory of the origin of pilonidal sinus has become reduced to a corporal’s guard. That, in rare instances, a sinus in the anococcygeal area is congenital must be allowed, but in these cases of proven congenital origin the sinus is not necessarily pilonidal. It could be a sinus connected with a postanal dermoid, referred to above, or a sinus resulting from a persistent caudal remnant of the original neural canal. The latter occurs in the sacral rather than the coccygeal region, and is definitely connected with the spinal theca. On this account, meningitis from an extradural abscess may occur in a child.

  The reasons which support the acquired theory of origin of pilonidal sinus can be summarised as follows.

 

  Interdigital pilonidal sinus is an occupational disease of hairdressers, the hair within the interdigital cleft or clefts being the customers’. Pilonidal sinuses of the axilla and umbilicus have also been reported.

  The age incidence of the appearance of pilonidal sinus (82 per cent occur between the ages of 20 and 29 years) is at variance with the age of onset of congenital lesions.

  Hair follicles have almost never been demonstrated in the walls of the sinus.

  The hairs projecting from the sinus are dead hairs, with their pointed ends directed towards the blind end of the sinus.

  The disease mostly affects men, and hairy men most frequently.

      Recurrence is common, even though adequate excision of the track is carried out.

The mode of origin of a pilonidal sinus is now believed to he as follows: on sitting, the buttocks take the weight of the body, and move independently, or together. Hairs broken off by friction against clothing, and shed short hairs, whether originating from the nape of the neck, back, or buttocks, tend to collect in the cleft of the nates and/or a postanal dimple. Furthermore, it is suggested that the use of toilet paper may contribute to hair entangled in faecal matter being swept into the cleft; pilonidal sinus is extremely rare in those races that employ ablution after defecation. By reason of the shearing action of the buttocks, which is increased by sitting on a hard seat, and especially by vibration of a vehicle, loose hair travels down the intergluteal furrow, to penetrate the skin or the open mouth of a sudoriferous gland, such glands being more active in early manhood. It is not yet clear whether the initial entry of hairs through the skin is a primary event, or follows the softening of the skin due to pustular or other forms of dermatitis. Once a sinus has formed, intermittent negative pressure of the area may suck other loose hairs into the pit. So common was pilonidal sinus among jeep riders in the 1935—45 war, that it became known as ‘jeep bottom’.

Pathology

The sinus extends into the subcutaneous planes as an infected track. Branching side channels are not infrequent. A stratified squamous epithelial lining, of varying degrees of integrity, is found in about half the cases. Hair shafts are found either lying loose in the sinus, embedded in granulation tissue, or deep in mature scar tissue in three-quarters of the cases. Foreign-body giant cells are common.

Clinical features

There is a chronic or recurring sinus in the midline about the level of the first piece of the coccyx. Typically, a tuft of hair projects from its mouth. The discharge from the sinus or sinuses is often bloodstained, and contains foul sebum and sometimes hairs. Secondary openings may be present on either side of the midline, often far out on to the buttocks or in the perineum.

As has been indicated already, symptoms usually com­mence during the third decade; patients presenting later in life nearly always give a history dating back to this period.

Males with this condition outnumber females by four to one, the females being on an average 3 years younger than the males; this corresponds to the earlier maturation of the female. The condition rarely occurs in blonds; many of the patients are exceptionally hairy and are usually obese. In spite of the preponderance in dark-haired persons, whose hair is stiffer than the silky blond (Oldham), the condition is practically confined to white races. The complaint is of a discharge, pain or a tender swelling at the bottom of the spine. Even at the height of an attack of inflammation the constitutional symptoms are slight. Often there is a history of repeat­ed abscesses in the region that have discharged spontaneously or have been incised. The primary sinus may have one, or as many as six openings, all of which are strictly in the midline between the level of the sacrococcygeal joint and the tip of the coccyx. Unlike a fistula in ano, the sinus passes upwards and forwards towards the sacrum. It does not reach bone, but ends blindly near the bone. When an abscess forms it may discharge through a primary sinus; more frequently it points and bursts, or is incised to one side of the midline (usually the left), thus forming a secondary sinus.

Conservative treatment

Patients reporting for the first time with mild symptoms can sometimes he cured by conservative measures, which consist of cleaning out the track, removing all hairs from the area, followed by frequent washing of the parts with a detergent and water, and applying equal parts of witch hazel (liq. ext. hamamelis) and alcohol. Long sitting, e.g., driving a car, is avoided if possible. These measures, tried on a large scale in the US Army, proved tolerably successful — more successful than similar attempts in civil life, because the sufferer could be relegated to duties that were unlikely to aggravate the condition.

Treatment of an acute exacerbation (abscess)

If rest, baths, local antiseptic dressings and the administration of a broad-spectrum antibiotic fail to bring about resolution, the abscess should be opened through a comparatively small incision. Provided all hairs and granulation tissue are removed from the abscess cavity, there is some prospect of curing the lesion (Millar). After it has been cleaned out, the track can be destroyed by careful instillation of pure phenol solution (Maurice). In all other circumstances, an elective operation must be planned.

Operation should be performed only when the inflammation has been controlled by the measures indicated already.

The patient is placed on the operating table, for preference in the ‘jack-knife’ position. Methylene blue is injected into the sinus to colour all the tracks, the nozzle of the syringe being pressed against the opening to obtain some pressure. Variations in operative technique include the following.

Lay open the tracks, remove all debris and hair, and suture the edges to the skin, thus marsupialising the sinus. This procedure yields a good, hairless scar.

Excise all of the tracks, as stained by blue dye, meticulously secure haemostasis by diathermy and catgut ligature and, using sutures, coapt the subcutaneous fat and skin very accurately and institute a drain and suction (i.e. Redivac) for 48 hours to remove blood and serum. In cases of extensive sinus formation, primary cover may be achieved by rotating a flap of skin and fat.

Excise all of the tracks as stained by the blue dye and, after securing haemostasis as above, pack the wound. The following day the whole dressing is removed, and daily baths and moist dressing are instituted until the wound heals by granulation. A silastic elastomer pack is particularly useful for dressing the wound as it can be removed, washed and reinserted by the patient, and ensures that the wound heals from below. Epithelialisation can sometimes be speeded up by skin grafting. Immediately after operation, the patient should avoid sitting on the wound. Subsequently, the scar may require protection from further incursions of hair by selective hair-trimming. The recurrence rate after primary closure may be as high as 50 per cent without meticulous technique.

  Recurrent pilonidal sinus. Three possibilities account for this disap­pointment:

a diverticulum of the main channel has been overlooked at the primary operation;

new hairs enter the skin or the scar;

when the natal fold is deformed by scarring, the least trauma causes tearing of the scar, and the resulting crevice becomes contaminated with coliform and cutaneous bacteria.

An alternative approach to circumvent the incident of recurrence has been to ensure that the sound closure is to one side of the midline (Karydakis); this method has been reported as having a high rate of success. Yet another recently described technique said to have a high incidence of success is that described by Bascom. The procedure involves an incision lateral to the midline which allows the chronic abscess cavity robe scrubbed free of hair and granulation tissue (Fig. 61.16). Removal of the small midline pits is carried out with small (7 mm) incisions (Fig. 61.17). The lateral wound is then left open, but the midline incisions are closed (Fig. 61.18).