From MedlinePlus Genetics
The upper part of the body can also be affected. Some people with caudal regression syndrome have a heart condition or hearing problems.

People with caudal regression syndrome may have abnormal twisting (malrotation) of the large intestine, an obstruction of the anal opening (imperforate anus), soft out-pouchings in the lower abdomen (inguinal hernias), or other malformations of the gastrointestinal tract. Affected individuals are often constipated and may have difficulty with bowel control.

Genital abnormalities in people with caudal regression syndrome can include the urethra opening on the underside of the penis (hypospadias) or undescended testes (cryptorchidism). Some affected people may have an abnormal connection between the rectum and vagina (rectovaginal fistula). In severe cases, people with this condition may have underdeveloped genitalia (genital agenesis).

 

Abnormalities in the genitourinary tract in people with caudal regression syndrome are diverse. Urinary tract problems can result from abnormalities in the lowest part of the spinal cord, which contains the nerves that control bladder function. Damage to these nerves can cause a condition called neurogenic bladder, which makes it difficult to control the flow of urine. In addition, the kidneys may be malformed in people with caudal regression syndrome; defects include a missing kidney (unilateral renal agenesis), kidneys that are fused together (horseshoe kidney), or duplication of the tubes that carry urine from each kidney to the bladder (ureteral duplication). These kidney abnormalities and neurogenic bladder can lead to frequent urinary tract infections and the backflow (reflux) of urine into the kidneys, which damage the kidneys and can cause progressive kidney failure.

Mobility in people with caudal regression syndrome is varied. Some individuals with the condition walk independently, and others require mobility aids, such as braces, crutches, walkers, or wheelchairs.

Individuals with caudal regression syndrome may have small hip bones. The buttocks tend to be flat and dimpled. The bones of the legs are typically underdeveloped, and the joints in the lower limbs may be unusually stiff and difficult to move. In some affected individuals, the legs are bent with the knees pointing out to the side and the feet tucked underneath the hips (sometimes called a frog leg-like position). These individuals may have webbed skin behind their knees. In other affected individuals, the knees may not bend, and the legs remain in a straight position. Their feet may be inward- and upward-turning (clubfeet) or outward- and upward-turning (calcaneovalgus). Some people with caudal regression syndrome have reduced or excessive sensation in their lower limbs. Sensitivity differs from person to person and from one area of the limb to another.

In people with this disorder, the bones of the lower spine (vertebrae) are misshapen or missing. The end of the spinal cord, the bundle of nerves and cells protected by the vertebrae, may also be malformed or missing. Sometimes, the spinal cord is abnormally connected (tethered) to nearby tissues. People with caudal regression syndrome can also have an abnormal curvature of the spine (lordosis or kyphosis). The spinal abnormalities may affect the size and shape of the chest, which very rarely leads to breathing problems.

Caudal regression syndrome is a disorder that impacts the development of the lower (caudal) part of the spine. The condition can affect many parts of the lower body, including the lower back and limbs, the genitourinary tract, and the gastrointestinal tract.  https://medlineplus.gov/genetics/condition/caudal-regression-syndrome