Normal vs. Abnormal Kidney Size: Signs, Risks, Complications

Like all other organs in the human body, the kidneys must be checked at all times in order to determine if there are any causes for concern. So naturally, many of us might wonder what a normal kidney size is, and what it means for our health.

What Is the Normal Kidney Size?

The average adult kidney size is around 10 to 12 cm which is roughly smaller than a clenched fist. But kidney size differs with age. To be more specific, refer to the bullet points below for the normal kidney size based on age group:

• Adult kidney size: 10-14 cm long for males and 9-13 cm long for females. The width ranges from 3-5 cm, 3 in antero-posterior thickness, and has a weight of 150-260 g. Usually, the left kidney is larger in size compared to the right kidney. 
• Child kidney size: It depends on their age and size. 
  • 0 to 12 months: 5 cm
  • 2 months to 6 months: 5.7 cm
  • 6 months to 1 year: 6.2 cm 
  • 1 year to 5 years: 7.3 cm 
  • 5 years to 10 years: 8.5 cm 
  • 10 years to 15 years: 10 cm 
  • 15 years old and above: the kidney size for this particular age group is similar to the normal kidney size of adults. 

Why Would a Kidney Shrink?

A shrinkage of a kidney is called kidney atrophy. Kidney atrophy happens for two main reasons:

• Congenital problem: the kidney does not fully develop since birth.
• The other reason happens after birth, and it can affect either one kidney or both kidneys. This happens when there is a low blood supply being sent to the kidney and/or the loss of nephrons. 

Kidney atrophy also happens due to blockage and chronic infections. This shrinkage can lead to health issues such as kidney disease. And the more it decreases in size, the more severe the effects would be to the kidney. If both kidneys happen to shrink then that will lead to kidney failure. 

Furthermore, small kidneys typically indicate an irreversible damage from a disease. In the Philippines, kidney shrinkage is commonly secondary to hypertension and diabetes, as well as long-standing kidney disease.

Why Would Kidneys Increase in Size?

A kidney that swells up is called hydronephrosis. This happens when there is a build-up of urine in the kidney. The urine is not drained out from the kidney due to blockage, and this can happen to both kidneys.

Hydronephrosis happens for various reasons such as:

• Congenital blockage 
• Blood clots
• Pregnancy
• Kidney stones
• Scarring of tissue from surgeries or injuries
• Non-cancerous enlarged prostate 
• Tumor or cancer 
• Urinary tract infection 

Large kidneys are likewise commonly seen in disease such as diabetes (during early stages of diabetic nephropathy), multiple myeloma and polycystic kidney disease.

How Would You Know If Your Kidney Size Is Abnormal?

In order to know if your kidney size is normal or not, you must go and see a doctor and have your kidneys checked via ultrasound or x-ray. The doctor will then measure and tell you if it is normal or not. 

After the doctor determines that your kidneys indeed decreased or increased in size, they might then perform further tests to check what caused this and proceed on suggesting appropriate intervention.

Complications 

If a person gets diagnosed with kidney disease or kidney failure, they can develop complications such as:

• Anemia
• Bone disease 
• High potassium 
• Heart disease
• Gout
• Fluid buildup
• Metabolic acidosis 
• Low calcium (in chronic kidney disease)
• High calcium (often associated with acute kidney injury)
• High phosphorus 

Learn more about Kidney Disease here.