Can You Be Born Without an Anus?

Roughly 1 in every 2,500 to 3,000 babies is born with an absent or malformed anal opening, a group of birth defects collectively called anorectal malformations. The most recognizable form, often called imperforate anus, means the normal passage from the intestines to the outside of the body simply never formed during fetal development. It is one of the more common congenital surgical conditions, it is correctable with surgery, and the outcomes vary widely depending on the severity of the defect and whether other organs are also affected.

How Common Is It

A national birth cohort study in England identified 3,325 infants with anorectal malformations among nearly 9.5 million live-born singletons, putting the birth prevalence at about 3.5 per 10,000 live births.¹ A U.S. hospital series found a similar rate of about 1 in 2,500.² The condition is slightly more common in boys than girls. Some epidemiological data even suggest the birth prevalence of imperforate anus has been slowly increasing over time, though the reasons for that trend are not entirely clear.³

These are not vanishingly rare numbers. A large maternity hospital would expect to see several cases a year, and pediatric surgeons who specialize in the condition accumulate substantial experience with it over a career. About six in ten of the cases identified in the English cohort were classified as “complex,” meaning the malformation involved more than just a missing anal opening.¹

What the Defect Actually Looks Like

The term “imperforate anus” makes it sound like one condition, but the reality is a spectrum. At the mildest end, a baby might have a very narrow or slightly misplaced anal opening (anal stenosis). At the other extreme, the rectum may end as a blind pouch deep in the pelvis, with no connection to the skin surface at all. In between, the rectal pouch may stop just short of the skin or may connect abnormally to another structure through a passage called a fistula. In boys, fistulas commonly connect the rectal pouch to the urinary tract. In girls, fistulas frequently open into the vagina or the vestibule between the vagina and the urethra. In the most severe form, the urinary, genital, and intestinal tracts all share a single opening, a condition called persistent cloaca.

These distinctions matter enormously for treatment and prognosis. A “low” malformation, where the rectal pouch sits close to the skin surface, is much simpler to repair and carries a better outlook for normal bowel control than a “high” malformation, where the pouch ends well above the muscles of the pelvic floor.

Why It Happens

The anal canal normally forms during early pregnancy when the hindgut, the tube that will become the colon and rectum, grows downward and fuses with a shallow pit on the skin surface. When that process is disrupted, the result is some form of anorectal malformation.⁴ Research in mice has shown that signaling through the Sonic hedgehog (Shh) pathway is essential for this process. Mice lacking the Shh gene develop persistent cloaca, while mice missing certain downstream genes develop imperforate anus with abnormal fistulas, closely mirroring what doctors see in human babies.⁵

In humans, a recent genetic study identified several candidate genes, including SOX9 and MFHAS1, that may contribute to the malformation.⁶ A meta-analysis of genetic factors found a strong association between anorectal malformations and various congenital syndromes, reinforcing the idea that genetic disruptions play a significant role.⁷ Still, most isolated cases do not follow a clear single-gene inheritance pattern, and the condition rarely runs in families in any predictable way.

Environmental factors also seem to play a role. A systematic review and meta-analysis of parental risk factors found that maternal obesity roughly doubled the odds, pre-gestational diabetes increased the odds more than fourfold, and gestational diabetes nearly doubled them. Paternal smoking was also associated with about a 50 percent increase in risk, though maternal smoking showed no consistent link.⁸ A German study added that mothers of affected children were more likely to have had urogenital infections during pregnancy and less likely to have taken folic acid supplements.⁹ None of these factors are deterministic on their own, and most babies born to parents with these risk factors are perfectly healthy. The cause in any individual case is usually unknown.

The Condition Rarely Comes Alone

One of the more important things to understand about anorectal malformations is that they often travel with other birth defects. In one large series, about two-thirds of patients had at least one additional congenital abnormality.¹⁰ The most commonly affected systems are the urogenital tract and the skeleton. A study of 174 patients found that among those with associated malformations, urogenital defects appeared in about 81 percent and skeletal abnormalities in about 46 percent, followed by cardiovascular and digestive system problems.¹¹

A well-known pattern is the VACTERL association, where anorectal malformations co-occur with vertebral defects, cardiac anomalies, tracheo-esophageal fistula (an abnormal connection between the windpipe and food pipe), kidney problems, and limb differences. About 15 percent of babies with anorectal anomalies meet the criteria for the full VACTERL association, and many more have one or two of the component features.¹² This is why any baby diagnosed with imperforate anus immediately gets a thorough workup of the heart, kidneys, spine, and esophagus. Finding and managing those associated conditions early can be just as important as repairing the anorectal defect itself.

How It Is Diagnosed

Most cases are picked up right after birth during the newborn physical exam. A nurse or doctor examining the baby notices there is no visible anal opening, or that the opening is in the wrong position. In boys the finding is usually obvious; in girls, a fistula opening into the vestibule can sometimes look close enough to normal that the diagnosis is briefly delayed.

Prenatal detection is possible but unreliable. On ultrasound, the normal anal canal produces a characteristic “target sign.” Researchers have described a “line sign” that replaces the target sign in fetuses with imperforate anus, successfully identifying 16 out of 19 cases in one study, though there were still false negatives.¹³ Prenatal diagnosis is more likely when the malformation comes with other detectable anomalies, such as an absent kidney or spinal defect. After birth, imaging with transperineal ultrasound helps determine whether the malformation is low or high, which directly guides the surgical approach.¹⁴

Surgical Repair

Every baby born with an imperforate anus needs surgery. The timing and complexity depend on the type of malformation. For low malformations where the rectal pouch is close to the skin, a surgeon can often perform a limited procedure in the newborn period, creating an anal opening and pulling the rectal pouch down to the skin surface. For high malformations, the standard approach typically involves three stages: first, a temporary colostomy (bringing the colon to the abdominal wall so stool can pass safely); then, weeks or months later, a definitive reconstruction called a posterior sagittal anorectoplasty, or PSARP, where the surgeon carefully places the rectal pouch within the muscle complex that controls continence; and finally, closure of the colostomy once healing is confirmed.¹⁵

The PSARP technique, pioneered in the 1980s, transformed outcomes for this condition. By approaching from behind and meticulously identifying the pelvic muscles, surgeons can position the new anal canal precisely within the muscle sling that provides voluntary control. Better imaging and improved understanding of pelvic anatomy have refined the technique over the decades.¹⁶

Long-Term Bowel Function

Surgery creates an anal opening, but it cannot always create perfectly normal bowel control. How well bowel function works afterward depends heavily on the original anatomy. Children born with low malformations fare considerably better than those with high ones, because the muscles and nerves that control continence tend to be more intact. In one follow-up study, about a third of patients who had PSARP were fully continent, about a third had some degree of stool soiling, and roughly a third dealt primarily with constipation.¹⁷

A study of adult patients found that difficulties sensing an impending bowel movement were common, affecting about 38 percent. Trouble holding back stool affected about 40 percent, and about three-quarters of patients had experienced at least one soiling accident in the past year. Those with high or intermediate malformations were significantly more likely to have frequent daytime soiling than those with low malformations.¹⁸ Persistent fecal incontinence beyond childhood remains common in this population.¹⁹

The range reported across studies is wide. A systematic review found that fecal incontinence prevalence among adolescents and young adults ranged from about 17 to 77 percent, and chronic constipation ranged from about 22 to 87 percent, depending on the study population and severity of the original malformation.²⁰ These are not small numbers, and they underscore that for many patients, managing bowel function is a lifelong task rather than something that ends after surgery.

Bowel Management Programs

For patients who do not achieve natural continence, structured bowel management programs can be transformative. These programs typically involve daily enemas or laxative regimens timed so that the colon empties at a predictable time each day, keeping the patient clean between sessions. The approach is individually tailored: the type of enema, its volume, and its additives are adjusted until the right recipe is found.

The results are genuinely encouraging. In one large program, about 88 percent of patients on enemas were clean by the end of an initial management week, and about 70 percent remained clean at one-year follow-up. The program also demonstrated significant improvement in quality-of-life scores.²¹ An earlier series reported success rates above 90 percent for patients with constipation-predominant issues and 88 percent for those with loose-stool issues.²² A multi-institutional review found that about 40 percent of children on a bowel management program were toilet trained, while roughly half still reported some daytime accidents.²³ Still, even when full independence is not achieved, the daily structure of these programs gives children and families a sense of control and drastically reduces the social burden of unpredictable soiling.

Urinary and Sexual Health in Adulthood

Because anorectal malformations so frequently come with urogenital abnormalities, problems with urinary and sexual function are common in adults who were born with the condition. A systematic review estimated that about 16 percent of adults after repair had urinary incontinence, and about 36 percent had lower urinary tract symptoms or neurogenic bladder dysfunction.²⁴ The same review found that about half of women reported some degree of sexual dysfunction, about 12 percent of men had erectile difficulties, and about 16 percent had ejaculatory dysfunction. The birth rate among the population studied was about 20 percent, lower than would be expected in the general population.²⁴

Spinal defects, which are common in this population, make these outcomes worse. Patients with spinal anomalies had lower voiding function and poorer urinary-related quality of life compared to those with normal spinal anatomy.²⁵ These findings make it clear that follow-up for anorectal malformations should extend well beyond the childhood surgery, into adolescence and adulthood, and should encompass urology and reproductive medicine as well as colorectal care.

Psychosocial Life

Living with a condition that affects bowel control, and sometimes bladder and sexual function, inevitably carries psychosocial weight. A systematic review of adult outcomes found that symptoms like soiling, rectal prolapse, and recurrent infections negatively affected health-related quality of life, with older patients, women, and those who still had a stoma reporting poorer outcomes.²⁶ One study of adults found that about a third of those with high or intermediate malformations occasionally dealt with fecal soiling, though the rest reported good enough bowel function to manage school or work without major interference.²⁷

An interesting finding from the pediatric literature is that children with imperforate anus often report being happy and optimistic. In one study, affected children actually reported liking school more and having better relationships with classmates than controls. Parents, however, noted more emotional and behavioral concerns, suggesting a gap between the child’s internal experience and the parent’s worry. Teachers corroborated the children’s own positive self-assessment rather than the parents’ concerns.²⁸ The takeaway: kids with this condition often adapt remarkably well, though that does not mean families do not carry significant stress.

Challenges in Low-Resource Settings

In wealthy countries with well-equipped neonatal units, imperforate anus is usually identified within hours of birth and treated according to well-established protocols. The picture looks very different in many low- and middle-income countries, where babies frequently present late, sometimes already septic, because families live far from a hospital or because the condition was missed at a delivery without trained attendants. A review of the global burden noted that delayed presentation adds sepsis and other complications, leading to increased suffering and death that would be preventable with timely surgical care.²⁹

Even when surgery is available, follow-up can be a major problem. A study from a Sudanese referral center found that a quarter of colostomies needed to be redone due to complications, surgical-site infections were common, and the post-operative dilation program (a critical part of preventing scar narrowing) suffered from the lack of systematic follow-up. Only 46 percent of patients were able to have their colostomy closed, largely because families could not afford to travel back to the hospital. Poverty and distance, not surgical technique, were the main barriers to good outcomes.³⁰

Transitioning to Adult Care

One gap that is only recently getting attention is what happens when a child who was operated on as a baby grows up and ages out of pediatric care. Adult gastroenterologists and colorectal surgeons may have limited experience with this condition, and the patient may not know how to navigate the adult healthcare system for a problem they have had since birth. A systematic review of transitional care found that the key solutions include fostering the young adult’s autonomy, running joint pediatric-adult clinics, and establishing structured transition programs with standardized guidelines.³¹ In practice, many patients fall through the cracks, quietly managing ongoing symptoms on their own and sometimes not seeking care for urological or sexual problems because they assume nothing can be done. Building awareness, both among adult providers and among patients themselves, that long-term specialized follow-up is available and beneficial remains an ongoing effort.

The Condition in Animals

Anorectal malformations are not unique to humans. They have been documented in dogs, cats, horses, and other species. In dogs, four distinct types have been described, ranging from a narrowed anal opening to complete discontinuity between the rectum and the anal canal. Certain breeds, including miniature and toy poodles and Boston terriers, appear to be more susceptible, and the condition is more common in female dogs. The parallels with human disease have made animal cases useful for studying the underlying developmental biology, and the mouse models used to study the Sonic hedgehog pathway are one of the clearest examples of how animal research has advanced understanding of this human condition.