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Anal atresia
Anal atresia is a malformation present at birth: the orifice of the anus has not formed. The lamb's digestive tract ends in a dead end and nothing can come out. From the outside, there is nothing to see. The lamb is born normal in appearanc...
What is it?
Anal atresia is a malformation present at birth: the orifice of the anus has not formed. The lamb's digestive tract ends in a dead end and nothing can come out. From the outside, there is nothing to see. The lamb is born normal in appearance, gets up, suckles, and appears vigorous for a day or two. This is what makes the malformation so often discovered too late. Then everything stops: matter accumulates, the belly swells, the lamb grows in vain, stops sucking and dies in significant suffering within a few days. There are similar forms: sometimes the anus exists but the rectum is interrupted higher up, sometimes the intestine opens abnormally into the vagina in females, and the breeder then sees matter coming out through the vulva. Only an examination at birth can identify it in time. Lifting the tail of each newborn lamb takes two seconds and makes the difference between possible surgery and agony.
Key point
A lamb that has not passed a poop within a day of life and whose belly is swollen should be examined the same day. After two or three days, even surgery can do no more.
Commonly observed signs
These signs are neither exhaustive nor specific. Only a veterinarian can establish a diagnosis.
Related signs — each one links to its page:
No meconium, the first black and sticky droppings of the newborn, is found neither on the hindquarters nor in the straw.
When you lift the tail, you don't see an anal opening: the skin is smooth, sometimes with a simple rounded bulge that stretches when the lamb pushes.
In the first hours, the lamb appears normal and sucks: this false calm deceives the breeder.
From the first or second day, the stomach swells and becomes hard and painful to the touch.
The lamb pushes, arches, wags its tail without result.
Grinding of teeth, complaints, lamb lying down and getting up again and again.
Refusal to breastfeed, depression, then fluid coming up through the mouth or nose.
Lamb which ends up lying on its side, without reaction.
In some females, matter comes out through the vulva: the anus is absent but the intestine opens into the vagina.
When to consult without delay
This list does not replace veterinary advice. It gathers situations that justify a prompt consultation.
Causes and risk factors
This is a formation defect during the life of the fetus: the tissues which should normally open to create the anal opening have not separated.
The exact cause is not established in most cases. A hereditary part is suspected in certain lines, which encourages monitoring the descendants of a ram when several lambs are involved.
It is neither an infectious disease, nor the consequence of a fault of the breeder, nor something that can be caught.
The malformation can be isolated or be accompanied by other internal anomalies, particularly of the urinary tract, which only a veterinary examination can assess.
No clearly identified breeding factor: the malformation occurs without any link to diet, housing or season.
An accumulation of cases in the offspring of the same ram must, however, raise suspicion of a hereditary component and lead to discussion with the veterinarian.
The real aggravating factor is the lack of examination of the hindquarters at birth, which transforms a sometimes operable malformation into certain death.
Diagnosis and care
Diagnosis is the veterinarian's responsibility, based on clinical examination and laboratory tests. Care is decided case by case.
Diagnosis is made by simple inspection: lift the lamb's tail and check for the presence of the anal orifice.
The veterinarian then assesses what is most important for the lamb's future: the length of the missing segment. A cul-de-sac located just under the skin, which bulges when the lamb grows, is much more favorable than a deep interruption of the rectum.
In females, he checks whether the intestine opens into the vagina, which completely changes the course of action.
He looks for other associated malformations, particularly urinary ones, which can doom the lamb even if the anus is reconstructed.
It rules out other causes of a swollen belly without droppings in a newborn, in particular wet mouth syndrome, which is much more common and is treated quite differently.
This examination must be carried out quickly: after a few days, the intestine is distended and damaged, and the lamb is too weakened to support an intervention.
Treatment
There is no medical treatment: neither laxative, nor enema, nor massage creates an orifice which does not exist. Any such attempt only delays the decision and causes the lamb to suffer.
When the cul-de-sac is superficial, a surgical intervention carried out by the veterinarian makes it possible to open the orifice and restore the passage. It must be done very early, before the intestine is distended and the lamb becomes weak.
The consequences require monitoring: a stricture may appear during healing and the lamb may have difficulty controlling its stools.
When the interruption is deep, when the intestine opens into the vagina, or when other malformations are present, reconstruction is not reasonably achievable in breeding and euthanasia avoids long and painful agony. It's a difficult decision but one that comes down to respect for the animal.
Never wait to see if it goes away on its own: it never goes away on its own.
Under no circumstances should you attempt to incise the lamb's hindquarters with a knife or blade: the exact position of the cul-de-sac, the depth and the reconstruction of the sphincter cannot be improvised, and the lamb would die of infection.
Treatment depends on the cause and the animal's condition: it must be determined by a veterinarian. No self-medication.
Prevention
There is no way to prevent this malformation from occurring.
The only real lever is screening at birth: lifting the tail of each lamb and checking the anal orifice, at the same time as disinfecting the navel, checking the eyes and checking the feeding. This comprehensive two-minute examination per lamb is the best habit of a lambing season.
Monitor, in the days that follow, that each lamb passes droppings.
Note the cases and the origin of the lambs concerned; If several occur in the offspring of the same ram, talk to the veterinarian before using it again.
Possible complications
Distention then perforation of the intestine, with generalized infection of the abdomen.
Intense and prolonged pain.
Inevitable death within a few days in the absence of intervention.
After surgery: narrowing of the reconstructed orifice, incontinence, local infections.
In females with communication between intestine and vagina, genital infections and animal unfit for reproduction.
When to see a veterinarian
A newborn lamb has no visible anal opening: call the veterinarian immediately, intervention is only possible very early.
A lamb aged one to three days has not passed any poop and its belly is swollen.
He pushes, arches and complains without evacuating anything.
Material comes out through the vulva of a lamb.
He stops sucking and becomes depressed: it's an emergency.
Several lambs from the same campaign have this malformation: talk to the veterinarian before using the same ram again.
Prognosis
Good when the cul-de-sac is superficial, the intervention is carried out in the very first hours and there is no other malformation: the lamb can live normally.
Reserved in cases of post-operative stricture or persistent incontinence.
Without intervention, the outcome is always fatal.
Deep forms and communications with the vagina have a very unfavorable prognosis in breeding conditions.
Frequently asked questions
My lamb does not have an anus, can we operate on it?
Sometimes yes, if the cul-de-sac is located just under the skin and if we intervene very early. The veterinarian is the only one who can judge the depth of the interruption and the presence of other malformations. Every hour counts: call now.
Is it my fault, because of the sheep's diet?
No. This is a formation defect during gestation, the exact cause of which is not established. It is neither a disease that can be caught nor the consequence of a driving error. A hereditary part is suspected in certain lines, which only justifies monitoring the ram's descendants.
Can an enema or oil unblock the lamb?
No, absolutely not. There is no cork to soften: there is simply no orifice. These attempts only cause the lamb to suffer and delay the only useful decision, which is the immediate veterinary examination.
How to avoid discovering one too late?
By getting into the habit of lifting the tail of each lamb at birth, when you are already disinfecting the navel and checking that it is suckling. This check takes two seconds and transforms a hopeless case into a sometimes operable one.
References
Content reviewed by the TunisieVet editorial team · Updated 11 August 2026
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