As the name of the syndrome suggests, the main symptoms of loin pain hematuria syndrome (LPHS) are:

• Loin pain: the pain is often described as a burning or throbbing and for some can worsen with exercise or when lying down flat on their back (facing upward). The pain may be felt on one side of the body (unilateral) or both sides (bilateral).
• Blood in the urine (hematuria): the blood may be noticeable in the urine or may only be seen under a microscope. Although larger amounts of blood in the urine are usually associated with severe pain episodes, in some cases, the blood may clear up even during a pain episode.

Other symptoms of LPHS may include:

• Nausea and vomiting during episodes of pain
• Low-grade fever (up to 101°F)
• Painful urination

LPHS can affect people differently. The episodes of pain and blood in the urine can last hours, weeks, or may be constant. Episodes can range from happening several times a year to being chronic with little or no relief between episodes.

The cause of primary loin pain hematuria syndrome (LPHS) is not known. The blood in the urine associated with LPHS is believed to come from the glomeruli, which are the tiny blood filtering units of the kidneys. Normally the blood is filtered in a glomerulus and the waste and extra fluid is passed into a connected tubule to become urine. However, the majority of kidney biopsies from people with LPHS also find red blood cells in the tubules, suggesting at least some of the glomeruli are damaged or abnormal, causing them to be leaky. It is not clear however why sometimes the kidney biopsies do not find red blood cells in the tubules. The pain associated with LPHS is believed to come from the kidneys, but how the pain develops is not understood.

About half of the people with LPHS have had kidney stones in the past. Some scientists, therefore, suspect that the formation of crystals and/or stones in the kidney may also contribute to LPHS as the crystal or stones may block or injure the renal tubules (the long narrow tubes in the kidney that concentrate and transport urine).

Sometimes loin pain hematuria syndrome is related to other conditions. When the cause of LPHS is known, some experts refer to this as LPHS, type 1 or secondary LPHS.

Loin pain hematuria syndrome (LPHS) is diagnosed when all other nonglomerular causes of the symptoms have been ruled out (known as a diagnosis of exclusion). Glomeruli are the blood cleaning units of the kidneys and are believed to be the source of the bleeding in LPHS. In addition to ruling out other possible causes, the episodes loin pain and blood in the urine must persist or be recurrent for at least 6 months and not associated with blockages due to kidney stones.

Tests to rule out other possible causes of loin pain and blood in the urine may include:

• Urine culture to rule out infection
• Urinalysis to check for damage to the filtering units of the kidney (glomerular disease)
• Endoscopy of the urethra and bladder (cystoscopy) and/or CT scan to rule out kidney stones, tumors, and cysts
• Special X-ray or CT scan with dye (angiography or CT angiography) to rule out problems with the kidney's blood vessels, such as a tangle of veins and arteries (arteriovenous malformations or AVM)) or benign tumors made up of a build up of blood vessels (hemangiomas)
• Upper urinary tract endoscopy (flexible ureteroscopy) to rule out problems with the tubes that carry the urine from the kidneys to the bladder (ureters)
• Special blood tests to rule out bleeding disorders

A kidney biopsy may be performed to rule out secondary LPHS if there are any signs of glomerular disease, such as microscopic blood in the urine or abnormal shaped blood cells with the presence of protein in urine (proteinuria), and/or increased creatinine levels in the blood. In some cases, a kidney biopsy may also be recommended to evaluate the structure and function of the kidney.

At this time, there is no disease-specific treatment or cure for loin pain hematuria syndrome (LPHS), since the cause of the disease is not understood. Unless the cause of glomerular disease is treatable, the treatment of primary and secondary LPHS focuses on pain management.

People with LPHS may be told to avoid activities that increase or trigger their pain, such as exercise, riding in a car, or lying on their back. Pain management may include medications, such as non-opioid pain pills (analgesics), narcotics, or opioids depending on the severity of pain, and/or possibly a nerve block or transcutaneous electrical nerve stimulation (TENS). Medications may also be used to treat nausea and vomiting if needed. If there is a history of kidney stones or build of calcium deposits, recommended treatment may include management of the amount of liquid a person drinks or changes in diet.

Limited evidence suggests that drugs that inhibit angiotensin may reduce the frequency and severity of episodes of loin pain and severe hematuria. Similarly, one study in 2009 found neuromodulation through implanted electrodes successfully reduced the pain in four women with LPHS, but it is unclear if neuromodulation has been tested further as a treatment for LPHS.

People with debilitating pain who do not respond to other therapies may be offered surgery, such as renal denervation, nephrectomy, or kidney auto-transplantation; however, surgical treatment of LPHS is controversial as some studies suggest that it has limited value for treating the recurrent pain and the possible complications of the procedures may outweigh the benefits.

While LPHS does not normally affect the function of the kidneys or cause other health problems, the pain associated with LPHS can be chronic and/or severe and may seriously decrease a person's quality of life. Long term treatment with narcotics and opiates can lead to drug addiction, which can add further social and medical issues. Due to the disabling nature of chronic, severe pain, those caring for a person with LPHS should watch for signs of depression and/or anxiety.

Currently, there are few long term studies to have a clear understanding of the course of LPHS, but two small, older studies, as well as the experience of specialists, propose the symptoms of LPHS will eventually get better spontaneously, however this can be after many years. Published cases and studies suggest a range for the duration of symptoms of 2-35 years.