Kidney stones, or renal calculi, are hard, crystallized deposits made of minerals and salts that form inside the kidneys. These stones can range from the size of a grain of sand to that of a golf ball, and their passage through the narrow urinary tract can cause intense pain. The question of whether kidney stones specifically cause diarrhea is a frequent one, given the close proximity of the urinary and digestive systems. This article addresses the relationship between kidney stones and diarrhea by examining the correlation and the underlying physiological mechanisms.
The Relationship Between Kidney Stones and Diarrhea
Kidney stones do not typically cause diarrhea. While a stone’s passage is known for triggering severe gastrointestinal upset, this distress more commonly manifests as pronounced nausea and vomiting.
The severe, fluctuating pain, known as renal colic, can disrupt the normal function of the digestive system, leading to a general bowel upset or dysmotility. This systemic stress response can occasionally result in diarrhea for some individuals, although it is not a defining characteristic of the condition. Furthermore, the medications used to manage the stone pain, particularly opioid-based analgesics, can alter bowel habits, sometimes causing constipation, but in other cases, leading to loose stools. In rare instances, a stone lodged very low in the ureter, near its entrance into the bladder (the ureterovesical junction), can irritate neighboring structures. However, the primary link between kidney stones and digestive issues remains the indirect effect of severe pain and the shared neurological pathways.
Shared Nerve Pathways and Referred Pain
The reason kidney stone pain causes such profound gastrointestinal symptoms lies in the body’s shared internal wiring, known as referred pain. Referred pain occurs because the nerve fibers carrying sensation from the internal organs converge with nerve fibers from other parts of the body at the same segments of the spinal cord. The brain then misinterprets the origin of the intense pain signal.
The kidneys, ureters, and the upper gastrointestinal organs are all supplied by nerves that originate closely together in the abdomen. Specifically, the sympathetic nerves from the kidney and ureter travel toward the spine, with many connecting to the celiac plexus, a dense network of nerves located near the aorta and behind the stomach and pancreas. When a kidney stone causes a blockage, the resulting pressure and spasm in the ureter send intense pain signals to the spinal cord and central nervous system. Because the nerves from the urinary tract share these nerve pathways with the digestive organs, the brain interprets these signals as originating from the stomach or intestines. This “cross-talk” is the physiological reason for the common and immediate experience of nausea and vomiting during a stone episode.
Recognizing the Primary Symptoms of Kidney Stones
The defining signs of a kidney stone center on the urinary tract. The most recognized symptom is renal colic, which is a sudden, sharp, and excruciating pain that often comes in waves as the ureter spasms around the stone. This pain typically begins in the flank, which is the side of the body between the ribs and the hip.
As the stone moves down the ureter, the pain location often shifts and radiates forward, moving toward the lower abdomen and groin. Depending on the stone’s position, the pain may also be felt in the testicles in men or the labia in women. Other recognized symptoms involve changes in urination patterns and appearance. Many patients experience hematuria, or blood in the urine, which can be visible (gross hematuria) or only detectable under a microscope (microscopic hematuria). The stone can also cause a frequent or urgent need to urinate and dysuria, which is pain or burning sensation during urination.
When to Seek Urgent Medical Care
Although most small kidney stones will pass naturally with supportive care, certain symptoms require immediate medical attention to prevent serious complications. A high fever, often accompanied by chills or rigors, is a sign that the stone may be causing an infection in the kidney or urinary tract, known as pyelonephritis. This condition is a medical emergency that necessitates immediate treatment with antibiotics.
Persistent and severe vomiting is another reason to seek urgent care, as it can quickly lead to severe dehydration, making it difficult for the stone to pass and potentially damaging the kidneys. Furthermore, the inability to pass urine, known as anuria, or a significant decrease in urine output, suggests a complete blockage of the urinary tract. This situation can cause urine to back up into the kidney, which requires prompt intervention to protect kidney function.