What Is A KUB X-Ray?

KUB X-ray stands for kidney, ureter and bladder X-ray.   This is an X-ray that may be the first step in diagnosing a condition of the urinary tract.  It is best for showing stones in the urinary tract.

What does a KUB X-ray show?

KUB X-rays do not directly show the kidneys, ureters and bladder.  They may be faintly seen at times, but often blend in with the surrounding soft tissues of the abdomen.  We diagnose conditions based on where we expect the structures of the urinary tract to be.  The X-ray will also show the bowel, bones and the lowest part of the chest.

KUB is best done to visualize stones.  Many stones can be seen on X-ray.  Stones can be located in the kidneys, along the ureters, and within the bladder.   We can diagnose stones in these locations because we know their expected location.  Sometimes we see shadows of the bladder and kidneys.

Does KUB show all stones of the urinary tract?

Stones in the kidneys can be single or multiple.  Many stones of the urinary tract can be seen on X-ray but there are exceptions.  Some stone types are not seen on X-ray and need CT to be diagnosed.  Stones can pass from the kidneys into the ureters and cause obstruction of the kidney.

Is KUB good if I am passing a stone?

Stones along the course of the ureters can often be seen with some exceptions.  We don’t see the ureters but know their location.  Stones will appear as bright white spots along the course of the ureters.  We don’t know how much obstruction of the kidneys there is with x-ray.  We can not see the kidneys directly to say how much obstruction there is.  We need an ultrasound or CT for that.

Bladder stones

KUB x-ray can also identify many stones in the bladder.  We don’t actually see the bladder but can see a stone as a white spot in it’s expected location.

Following kidney stones

KUB is also used to follow stones.  KUB X-rays are used to see if the stone has passed or if kidney stones are increasing.  Urology doctors may need to remove the stones if they persist, cause complications or continued symptoms.

What else can a KUB X-ray show?

KUB X-rays can also show the bowel.  That is an advantage when a patient presents with pain but we are not sure the cause is the urinary tract.  Sometimes a bowel disorder can be diagnosed that is confused for a urinary tract problem.  We can see bowel obstructions or blockages, ileus or poor function of the bowel, and at times, inflammatory conditions.

KUB X-ray can also show abnormalities of the the bones of the spine and pelvis.  Most commonly this is arthritis.  We can also diagnose conditions of the lowest part of the lungs which are often included.  KUB X-rays can also diagnose stones in the Gallbladder since the gallbladder is included.  We can also diagnose enlarged organs at times.

Why is a CT scan better than KUB X-ray?

KUB X-ray is primarily done to diagnose conditions of the urinary tract.  This is done most commonly to look for stones in the urinary tract.   CT scan of the abdomen and pelvis is a better test because we can see the entire urinary tract directly.  We can diagnose more conditions of the urinary tract like masses. CT will also show stones that the X-ray can not.  CT can also diagnose many conditions that are outside the urinary tract.

Advantages of KUB X-ray?

A KUB X-ray can also diagnose many other conditions.  It is quick, less expensive, and has a lower radiation dose than CT.  KUB X-ray is a quick way to begin an evaluation of the urinary tract.  The KUB also allows us to follow stones in the ureters for passage.   CT is often done after KUB for more detailed evaluation.