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).
The army of supporters of the congenital
theory of the origin of pilonidal sinus has become reduced to a corporal’s
guard.
•
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.
•
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).