The kidneys are bean-shaped organs about the size of a fist located in the back of the abdomen, just under the ribcage, on each side of the spine. The kidneys are part of the urinary tract and they function to remove excess fluids and waste from the body.
People can actually survive with only one kidney, as is the case in people born with only one kidney (unilateral renal agenesis) or people who donate a kidney. In fact, if you donate or lose a kidney, you still have 60 to 65 percent function. People only need 30 percent kidney function for normal survival.
It is not completely understood why we have two kidneys, but theories include:
- There is extra reserve of kidney mass in case of injury to a kidney
- Most animals who live on land have what is called “bilateral symmetry,” that is, everything is the same on both sides: two arms, two legs, two eyes, two ears, two lobes of the lungs, etc. and kidneys are an extension of this symmetry
What Are Types of Kidney Problems?
Common types of kidney problems include:
- Urinary tract infection (UTI)
- Kidney infection (pyelonephritis)
- Kidney stones
- Polycystic kidney disease (PKD)
- Blood clots in the kidney(s) (renal vein thrombosis)
- Bleeding in the kidney(s)
- Kidney tumor or cancer
- Kidney cysts
- Kidney swelling
- Kidney trauma
- Kidney failure called End Stage Renal Disease (ESRD)
What Are Symptoms of Kidney Problems?
Signs and symptoms something is wrong with the kidneys include:
- Pain in the sides, back, or belly
- Painful urination
- Blood in the urine
- Cloudy urine
- Fever
- Chills
- Nausea
- Vomiting
- Dizziness
- Diarrhea
- Constipation
- Fatigue
- Rash
What Causes Kidney Problems?
Causes of kidney problems include:
- Kidney stones
- High blood pressure
- Diabetes
- Glomerulonephritis
- Infections
- Inherited diseases such as polycystic kidney disease
- Overuse of some over-the-counter (OTC) pain killers
- Illegal drugs such as heroin
How Are Kidney Problems Diagnosed?
In addition to a physical examination and patient history, tests used to diagnose the cause of the kidney problems include:
- Glomerular filtration rate (GFR) blood test
- Urine tests
- Ultrasound
- Computerized tomography (CT) scan or magnetic resonance imaging (MRI) of the pelvis
- Pregnancy test to rule out pregnancy
What Is the Treatment for Kidney Problems?
Treatment for kidney problems depends on the cause.
Medications may help relieve pain, such as:
- Acetaminophen (Tylenol)
- Morphine (for painful kidney stones)
- Patients with known kidney problems should be cautious with pain medications that are filtered through the kidneys, because this may cause additional damage to the kidneys
Kidney infections (pyelonephritis) or urinary tract infections (UTIs) are usually treated with antibiotics.
Kidney stones may need to be surgically removed in some cases.
From 
Healthy Resources
https://www.kidneyfund.org/kidney-disease/kidney-problems/kidney-pain.html
https://www.niddk.nih.gov/health-information/urologic-diseases/kidney-infection-pyelonephritis
https://www.urologyhealth.org/urologic-conditions/kidney-stones
https://www.kidney.org/atoz/content/kidneydiscauses
https://www.uptodate.com/contents/anemia-caused-by-low-iron-in-adults-beyond-the-basics?search=iron%20deficiency%20anemia&source=search_result&selectedTitle=4~150&usage_type=default&display_rank=4
https://ukrocharity.org/2010/07/q-a-why-do-we-have-two-kidneys/
https://www.piedmont.org/living-better/the-kidneys-how-they-work-and-what-happens-when-they-dont
https://www.latrobe.edu.au/news/articles/2018/opinion/why-do-we-have-two-kidneys