--- title: "Sacral dimple in babies: when to check for tethered cord" description: "A dimple, hair tuft or lump on a baby's lower back: which skin markers need imaging, and how a tethered spinal cord can affect the bladder and bowel." lang: en url: https://kidsurologycare.com/conditions/sacral-dimple-tethered-cord/ --- [Bladder and urethra](/conditions/#bladder) # Sacral dimple and tethered spinal cord: when does a dimple need tests? A dimple, hair tuft or lump on a baby's lower back: which skin markers need imaging, and how a tethered spinal cord can affect the bladder and bowel. Written by: [Dr. Parviz Hajiyev](/doctor/), European Board-certified pediatric urologist (FEAPU). Quick answers Is a simple dimple dangerous? A small, single dimple in the midline close to the anus is almost always harmless. What needs tests? A large, deep or high dimple, a hair tuft, a lump, a skin tag, or several markers together. First test Spinal ultrasound in young babies, MRI if needed. Link with the bladder A tethered cord can later cause wetting, infections and constipation. ## What is a sacral dimple? Some babies have a small dimple low on the back, between the buttocks. This is called a **sacral dimple**. Most of the time it is a harmless skin feature and causes no problems. Sometimes, though, skin markers on the lower back point to a birth difference in the spine and spinal cord underneath. This is called **occult spinal dysraphism**: it cannot be seen from the outside because it is covered by skin. ## What is a tethered spinal cord? Normally the lower end of the spinal cord moves freely inside the spinal canal. In some conditions (a thickened or fatty filum, a fatty lump, a skin tract) the cord is held down at its lower end. As the child grows, the cord is stretched. This is called a **tethered spinal cord**. At birth there are usually no symptoms. Problems can appear later as the child grows, and if diagnosed late, some of them may not be reversible. This is why it is important to know which skin markers need tests. ## Which skin markers need tests? **Usually harmless (simple dimple):** - a single small dimple (roughly under 5 mm), - exactly in the midline, close to the anus (within about 2.5 cm), - no other skin changes nearby. In healthy babies with this kind of dimple, serious problems are very rare and tests are usually not needed. **Should be checked by a doctor:** - a large (over 5 mm) or deep dimple whose bottom you cannot see, - a dimple above the crease between the buttocks or off to one side, or several dimples, - a tuft of hair in the midline, - a soft lump under the skin (lipoma), - a skin tag (“little tail”), - a red or purple birthmark, - two or more of these together: the risk is clearly higher. ## Link with the bladder and bowel The nerves that control the bladder and bowel come from the very lowest part of the spinal cord. When the cord is stretched, these nerves may stop working properly. This can lead to [neurogenic bladder](/conditions/neurogenic-bladder/). In a child with a skin marker on the lower back, watch for: - not becoming dry after toilet training, or [daytime wetting](/conditions/daytime-wetting/) coming back after a dry period, - repeated urinary tract infections, - a weak stream or straining to pee, - stubborn constipation or soiling, - weakness in the legs, a change in walking, or a curve of the spine that is getting worse. ## Diagnosis - **Spinal ultrasound.** The first test in young babies, while the bones of the spine are not yet fully hardened. It is painless and needs no anesthesia. - **MRI.** The most accurate way to see the spinal cord. It is done when the risk is high, the ultrasound is abnormal, or an older child has symptoms. - **Bladder tests.** [Uroflowmetry](/tests/uroflowmetry/), measuring the urine left after peeing and, if needed, [urodynamics](/tests/urodynamics/) show how the bladder works. ## Treatment A tethered cord is treated by a neurosurgeon: the tissue holding the cord down is cut to free it (untethering). The decision depends on the child’s symptoms and the type of anomaly: - if neurologic, bladder or orthopedic problems are getting worse alongside a skin marker, surgery is usually done, - in children without symptoms, the benefits and risks of surgery are discussed carefully. Children who were dry before surgery mostly stay dry afterward, and some children who were already wetting improve. If bladder problems remain, the pediatric urologist continues treatment. ## Follow-up Whether or not surgery is done, children at risk are followed through childhood and the teenage years by a neurosurgeon, a pediatric urologist and an orthopedic surgeon. If you notice new changes in peeing, bowel habits or walking, do not wait for the next scheduled visit. ## When to seek urgent care If any of the following is present, do not wait for a routine appointment: call the doctor or go to the nearest emergency department. - Fluid or pus coming from the dimple, or redness and swelling around it - Fever with drowsiness or vomiting in a child with a skin marker on the lower back - New weakness in the legs, a sudden change in walking, or sudden loss of bladder control Call your local emergency number (112 in Europe, 911 in North America) Note for pediatricians and family doctors Occult (skin-covered) spinal dysraphism is the most common congenital spinal anomaly; about 50–80% of patients have midline skin stigmata, and symptoms are often absent at birth and appear later as neurologic, urologic and orthopedic problems. In a meta-analysis of 15 studies (6558 infants), occult dysraphism was found in 2.8% of infants with stigmata and neurosurgery was needed in 0.6%; with combined stigmata 10.5% (single stigma 2.3%), with an atypical dimple 8.8% (simple dimple 0.6%). A simple dimple is usually smaller than 5 mm, midline, within 2.5 cm of the anus and not associated with other stigmata; atypical features include size over 5 mm, depth, a position above the gluteal crease or off the midline, and multiple dimples. High-risk stigmata include hypertrichosis, a pedunculated skin tag and any midline mass including lipoma. Of 3884 healthy infants with a simple dimple, only 5 (0.13%) had surgery; Choosing Wisely Canada advises against imaging a midline dimple related to the coccyx in an asymptomatic child. Before ossification of the posterior arches, spinal ultrasound is the first-line test in infants, and MRI is the reference standard. ICCS: classic skin markers with progressive neurologic, skeletal or urologic findings are an indication for MRI and untethering, while in asymptomatic children the surgical risk should be weighed carefully. Urodynamic studies are recommended in every patient with spinal dysraphism (EAU/ERN). In one series with long-term follow-up after untethering, 80% of children were continent, and all children continent before surgery stayed continent. ## What happens at the visit? 1. We look closely at the lower back: the size, depth and position of the dimple and any other skin markers. 2. We ask about peeing, bowel habits, leg strength and walking, and examine the legs and spine. 3. If needed, we arrange spinal ultrasound or MRI, and uroflowmetry, a post-void residual measurement and urodynamics to check bladder function. [Book on WhatsApp](https://wa.me/994504443035?text=Hello%2C%20I%20would%20like%20to%20book%20an%20appointment%20about%3A%20Sacral%20dimple%20and%20tethered%20cord.)Pediatric Urology Center, Badam Medical Center, Baku ## Frequently asked questions My baby has a small dimple near the tailbone. Does he need an ultrasound? If the dimple is small, in the midline, close to the anus and there are no other markers, the risk is very low and tests are usually not needed. If it is large or deep, sits higher up, or there is hair, a lump, skin discoloration or a skin tag nearby, the doctor will order a spinal ultrasound or MRI. Up to what age can a spinal ultrasound be done? Ultrasound is useful only in young babies, while the bones of the spine have not fully hardened. Older children need MRI to see the spinal cord. My child was dry and is now wetting again. Could it be the spine? Usually not: daytime wetting has much more common causes. But if there is a skin marker on the lower back, together with leg weakness, a change in walking or stubborn constipation, the doctor will suggest checking the spine. ## Related topics - [Neurogenic bladder Bladder problems in spina bifida and spinal cord conditions Condition](/conditions/neurogenic-bladder/) - [Daytime wetting Overactive bladder, voiding dysfunction Condition](/conditions/daytime-wetting/) - [Constipation and the bladder Bladder and bowel dysfunction (BBD) Condition](/conditions/bladder-bowel-dysfunction/) - [Bedwetting Enuresis, nocturnal enuresis Condition](/conditions/bedwetting/) - [Urodynamics Bladder pressure measurement, cystometry Test](/tests/urodynamics/) - [Uroflowmetry Urine flow test Test](/tests/uroflowmetry/) Sources - [Choi SJ et al. Incidence of occult spinal dysraphism among infants with cutaneous stigmata and proportion managed with neurosurgery: a systematic review and meta-analysis. JAMA Netw Open, 2020.](https://pubmed.ncbi.nlm.nih.gov/?term=Incidence%20of%20occult%20spinal%20dysraphism%20among%20infants%20with%20cutaneous%20stigmata%20and%20proportion%20managed%20with%20neurosurgery%3A%20a%20systematic%20review%20and%20meta-analysis) - [Kucera JN et al. The simple sacral dimple: diagnostic yield of ultrasound in neonates. Pediatr Radiol, 2015.](https://pubmed.ncbi.nlm.nih.gov/?term=The%20simple%20sacral%20dimple%3A%20diagnostic%20yield%20of%20ultrasound%20in%20neonates) - [Tuite GF et al. Evaluation and management of tethered cord syndrome in occult spinal dysraphism: recommendations from the International Children's Continence Society. Neurourol Urodyn, 2018.](https://pubmed.ncbi.nlm.nih.gov/?term=Evaluation%20and%20management%20of%20tethered%20cord%20syndrome%20in%20occult%20spinal%20dysraphism%3A%20recommendations%20from%20the%20International%20Children's%20Continence%20Society) - [Frainey BT et al. Predictors of urinary continence following tethered cord release in children with occult spinal dysraphism. J Pediatr Urol, 2014.](https://pubmed.ncbi.nlm.nih.gov/?term=Predictors%20of%20urinary%20continence%20following%20tethered%20cord%20release%20in%20children%20with%20occult%20spinal%20dysraphism) - [Radic JAE et al. Choosing Wisely Canada: pediatric neurosurgery recommendations. Paediatr Child Health, 2018.](https://pubmed.ncbi.nlm.nih.gov/?term=Choosing%20Wisely%20Canada%3A%20pediatric%20neurosurgery%20recommendations) - EAU/ERN eUROGEN Joint Guidelines on Spinal Dysraphism in Children and Adolescents, 2025. This information is for educational purposes and does not replace medical advice. Decisions about your child’s treatment are made with the doctor after an examination. Updated: October 31, 2026 --- Information for parents and colleagues; it does not replace an in-person examination. Emergencies: call 103 (Azerbaijan, Kazakhstan, Uzbekistan) or your local emergency number.