Most cysts found on the liver and kidneys are simple, fluid-filled sacs that cause no symptoms and need no treatment. They are remarkably common: over half of people older than 50 have at least one kidney cyst on imaging, and roughly one in five adults screened by ultrasound turn out to have a liver cyst.1PubMed Central. Management of incidental renal masses: Time to consider contrast-enhanced ultrasonography2Scientific Reports. The prevalence and natural history of hepatic cysts examined by ultrasound: a health checkup population retrospective cohort study When cysts do become a problem, the causes range from random, age-related fluid collections to inherited genetic conditions that fill both organs with hundreds of cysts over a lifetime. Treatment options span the full spectrum from watchful waiting through drug therapy to transplantation, depending on the underlying cause and how far the disease has progressed.
Why Cysts Form in the First Place
The most common liver and kidney cysts are “simple” cysts, thin-walled sacs filled with clear fluid that develop sporadically as you age. No one fully understands why they appear, but they seem to arise when a small segment of a tubule (in the kidney) or a bile duct (in the liver) becomes blocked or dilates. These cysts tend to grow slowly, if at all, and the vast majority never cause trouble. Non-parasitic liver cysts show up in roughly 5% of the general population on routine imaging, though the figure climbs higher in studies using more sensitive ultrasound equipment.3PubMed Central. Management of symptomatic liver cysts
When cysts appear in both the liver and kidneys at the same time and in large numbers, the explanation is usually genetic. Autosomal dominant polycystic kidney disease (ADPKD) is the most well-known culprit, caused by mutations in either of two genes, PKD1 or PKD2, which encode proteins in the lining of kidney tubules.4PubMed Central. Detection of PKD1 and PKD2 Somatic Variants in Autosomal Dominant Polycystic Kidney Cyst Epithelial Cells by Whole-Genome Sequencing People with ADPKD frequently develop liver cysts too, and the liver involvement can sometimes be more debilitating than the kidney disease itself. A related condition, autosomal dominant polycystic liver disease (ADPLD), results from mutations in different genes (PRKCSH or SEC63) and produces numerous liver cysts with the kidneys largely spared.5Nature Genetics. A genetic interaction network of five genes for human polycystic kidney and liver diseases defines polycystin-1 as the central determinant of cyst formation
There is also a childhood-onset form called autosomal recessive polycystic kidney disease (ARPKD). It is far rarer, affecting roughly 1 in 20,000 births, and involves mutations in the gene PKHD1. Unlike ADPKD, ARPKD tends to cause progressive cystic changes in the kidneys alongside congenital hepatic fibrosis, a condition in which the liver develops scar tissue and abnormal bile ducts rather than the large fluid-filled cysts seen in adults.6Molecular Genetics and Metabolism. Hepatorenal findings in obligate heterozygotes for autosomal recessive polycystic kidney disease7Gastroenterology. Characterization of Congenital Hepatic Fibrosis in a Large Cohort of Patients With Autosomal Recessive Polycystic Kidney Disease
Infectious Causes That Mimic Simple Cysts
Not every cyst is either sporadic or genetic. In parts of the world where sheep and cattle farming are widespread, a parasitic infection called echinococcosis (hydatid disease) can produce cysts in internal organs. The parasite Echinococcus granulosus enters the body through food or water contaminated with eggs from dog feces. After hatching in the intestine, larvae travel through the bloodstream and settle in organs, most often the liver and then the lungs.8PubMed Central. Primary Renal Echinococcosis Kidney involvement is uncommon, accounting for about 2% of all hydatid cyst cases, which is part of why it gets missed. These cysts can grow quite large; one reported case involved a cyst over 12 centimeters across in the left kidney.9PubMed Central. Renal hydatid cyst; a rare infectious disease
Hydatid cysts are important to consider because they look very different from simple cysts under imaging and require entirely different treatment, often involving antiparasitic drugs and sometimes surgery. If you live in or have traveled to endemic areas (parts of the Mediterranean, Middle East, Central Asia, South America, or sub-Saharan Africa), a cyst that appears “complex” on ultrasound should prompt blood tests for Echinococcus antibodies before any drainage is attempted. Puncturing a hydatid cyst without precautions can cause a severe allergic reaction or spread the infection.
When Cysts Start Causing Symptoms
The frustrating reality is that most simple cysts, whether on the liver or kidneys, produce no symptoms at all. They are typically discovered when you get an ultrasound, CT, or MRI for something else entirely. It is estimated that over half of adults older than 50 have at least one renal mass, the majority of which are benign cysts.1PubMed Central. Management of incidental renal masses: Time to consider contrast-enhanced ultrasonography
Symptoms tend to develop only when cysts become large enough to press on surrounding structures. Large liver cysts can cause upper abdominal pain, nausea, vomiting, early satiety (feeling full after eating very little), and in some cases obstructive jaundice if a cyst compresses a bile duct.3PubMed Central. Management of symptomatic liver cysts Kidney cysts that grow large can produce flank pain, blood in the urine, or high blood pressure. In polycystic kidney disease, where hundreds of cysts develop over decades, the kidneys themselves become massively enlarged, sometimes several times their normal size, and the cumulative damage gradually destroys kidney function.
Cyst complications are uncommon but can be sudden. A cyst can become infected, bleed internally, or rupture. Infected cysts produce fever and localized pain and usually need antibiotics and sometimes drainage. A ruptured kidney cyst might cause sharp flank pain and blood in the urine that resolves on its own, though larger ruptures sometimes require intervention.
How Doctors Tell a Harmless Cyst from a Dangerous One
Simple cysts have a characteristic appearance on ultrasound: round, thin-walled, fluid-filled, with no internal echoes or solid components. When a cyst meets all of those criteria, it is overwhelmingly benign, and no further workup is needed.10Diagnostic and Interventional Imaging. Simple and complex renal cysts in adults: Classification system for renal cystic masses The concern arises when a cyst does not look simple: if it has thick walls, internal divisions (called septations), calcifications, or solid nodules, it needs closer evaluation.
For kidney cysts, the Bosniak classification has been the standard tool for more than three decades. Developed in the late 1980s, it groups cystic kidney lesions into five categories (I through IV) based on how complex they appear and how likely they are to be cancerous.11PubMed Central. Bosniak classification for complex renal cysts: history and critical analysis Categories I and II are benign and need no treatment. Category IIF (“F” for follow-up) has slightly more complexity and warrants periodic imaging. Categories III and IV carry real malignancy risk. A systematic review found that about half of Bosniak III cysts and roughly 89% of Bosniak IV cysts that went to surgery turned out to be malignant.12PubMed. Bosniak Classification for Complex Renal Cysts Reevaluated: A Systematic Review A reassuring finding from the same analysis: Bosniak IIF cysts that remained stable during surveillance had a malignancy rate under 1%, reinforcing that watching and waiting is safe in that group. However, the roughly 12% of IIF cysts that progressed to higher categories showed malignancy rates comparable to Bosniak IV.
For liver cysts, there is no single classification system as widely used as Bosniak, but the diagnostic approach follows similar logic. Ultrasound is the first-line tool, and most simple liver cysts are diagnosed there without further imaging. When findings are ambiguous, CT and MRI come next. MRI can detect features like thin septations, hemorrhage, and debris that CT sometimes misses, which helps distinguish rare but important lesions like mucinous cystic neoplasms from ordinary cysts.13Clinical Imaging. CT and MRI features differentiating mucinous cystic neoplasms of the liver from pathologically simple cysts In difficult cases, contrast-enhanced ultrasound and blood antibody tests can help sort out whether a cyst is parasitic, neoplastic, or truly benign.14PubMed Central. Evaluation of hepatic cystic lesions
Drug Treatments for Polycystic Disease
Simple cysts that cause no symptoms require no medication. But for people with ADPKD, where progressive cyst growth threatens kidney function over years and decades, drug treatment has become an important option. Tolvaptan, a drug that blocks a hormone receptor involved in cyst fluid secretion, is the first medication shown to meaningfully slow disease progression. In a landmark trial, tolvaptan reduced the rate of kidney growth to about 2.8% per year compared to 5.5% per year with placebo over three years, and it slowed the decline in kidney function.15PubMed Central. Tolvaptan in patients with autosomal dominant polycystic kidney disease Longer-term follow-up suggests the benefits persist with continued use.16PubMed. Long-Term Benefits of Treatment with Tolvaptan in Patients with Autosomal Dominant Polycystic Kidney Disease
Tolvaptan does come with trade-offs. It works by blocking the kidney’s ability to concentrate urine, so you produce large volumes of dilute urine and need to drink a lot of water to keep up. Liver toxicity is a known risk, requiring regular blood monitoring. It is generally recommended for patients whose disease is progressing but whose kidneys still have reasonable function.17PubMed Central. Tolvaptan in the treatment of autosomal dominant polycystic kidney disease: patient selection and special considerations
For the liver cyst burden in polycystic disease, somatostatin analogues (octreotide, lanreotide, and pasireotide) have been tested as a way to reduce liver volume. A crossover trial found that octreotide shrank liver volume by about 71 mL on average over the treatment period, while liver volume did not change with placebo.18PubMed Central. Reducing polycystic liver volume in ADPKD: effects of somatostatin analogue octreotide A network meta-analysis comparing the three drugs found that octreotide and pasireotide showed earlier directional effects on total liver volume at one year, while lanreotide’s effects appeared after longer treatment, and lanreotide was less effective at reducing liver growth than octreotide over a two-to-three-year period.19PubMed. Comparative Efficacy and Safety of Octreotide, Lanreotide, and Pasireotide in Autosomal Dominant Polycystic Kidney Disease and Polycystic Liver Disease: A Network Meta-Analysis With Real-World Evidence From the FDA Adverse Event Reporting System Database That said, a broader meta-analysis of randomized trials found the overall reduction in liver volume did not reach statistical significance, suggesting these drugs help some patients more than others and may be most useful for people with severely enlarged livers causing disabling symptoms.20Scientific Reports. The effects of somatostatin analogues on liver volume and quality of life in polycystic liver disease: a meta-analysis of randomized controlled trials
Aspiration and Sclerotherapy for Large Symptomatic Cysts
When a single large cyst is causing pain or compressing nearby structures, the most common first-line intervention is needle aspiration, sometimes followed by sclerotherapy. Under ultrasound guidance, a needle or small drainage tube is inserted into the cyst, the fluid is drained, and a sclerosing agent (often ethanol or concentrated glucose) is injected to destroy the lining and prevent the cyst from refilling. A study of this technique in elderly patients with giant hepatic and renal cysts found that cyst volume shrank by about 80% at three months for liver cysts and about 93% for kidney cysts, with one-year shrinkage rates exceeding 92% for liver cysts and 98% for kidney cysts.21PubMed Central. Giant cysts, no incisions: Ultrasound-guided sclerotherapy in the elderly
The main limitation is recurrence. Larger cysts are more likely to refill after aspiration and sclerotherapy, and the cyst’s maximum diameter was the strongest predictor of whether it would come back.21PubMed Central. Giant cysts, no incisions: Ultrasound-guided sclerotherapy in the elderly For that reason, aspiration and sclerotherapy work best for solitary or few large cysts in people who are not good candidates for surgery. For younger patients with a single troublesome cyst, surgery often provides a more durable result.
Surgical Options
The standard surgical treatment for symptomatic simple cysts is laparoscopic deroofing (also called unroofing or fenestration). The surgeon uses small incisions to cut away the exposed wall of the cyst, allowing it to drain freely into the abdominal cavity where the fluid is reabsorbed. For kidney cysts, retroperitoneal laparoscopic deroofing is a well-established technique. A refinement that packs perirenal fat tissue into the cyst bed after unroofing has shown lower recurrence rates and shorter drainage times compared to standard deroofing.22PubMed Central. The efficacy of retroperitoneal laparoscopic deroofing of simple renal cyst with perirenal fat tissue wadding technique
For liver cysts, laparoscopic deroofing is similarly effective. When cysts are very large, the surgery becomes more technically demanding because identifying the cyst boundary in relation to bile ducts and blood vessels is critical. Newer techniques using fluorescence imaging with indocyanine green dye help surgeons visualize bile ducts during the procedure, reducing the risk of bile leakage, a common complication of liver cyst surgery.23PubMed. Two cases of laparoscopic deroofing of giant liver cysts using indocyanine green fluorescence imaging Recurrence is the main concern after deroofing of hepatic cysts as well. One series combining deroofing with more radical excision of cyst walls in patients with multiple liver cysts reported recurrence in 5 out of the treated patients.24PubMed Central. Laparoscopic Management of Symptomatic Multiple Hepatic Cysts: a Combination of Deroofing and Radical Excision
For people with polycystic disease where the organs are riddled with cysts, deroofing individual cysts gives only temporary relief because new cysts keep forming. In these cases, more extensive surgery may be considered, including partial liver resection (removing the most affected portion of the liver) or, in extreme cases, organ transplantation.
Transplantation for End-Stage Polycystic Disease
When ADPKD destroys enough kidney tissue that dialysis becomes necessary, kidney transplantation is the treatment of choice, just as it is for other causes of kidney failure. But polycystic disease presents a unique scenario: some patients need both a liver and a kidney transplant because the polycystic liver has grown so large it causes severe pain, breathing difficulty, or malnutrition. A study of nine patients who underwent combined liver-kidney transplantation for polycystic disease found an overall survival rate of about 89%, and kidney function improved dramatically among the survivors, from a preoperative average filtration rate of about 20 mL/min to roughly 64 mL/min during follow-up.25Annals of Transplantation. Outcomes of Combined Liver-Kidney Transplantation in Polycystic Liver and Kidney Disease
The decision about whether to transplant the liver alone or both organs at once is not straightforward. An earlier study of 14 patients with polycystic liver and kidney disease found that 93% survived at least one year after liver transplant, but two of the eight patients who initially received only a liver transplant later needed a kidney transplant as well.26Transplantation. Liver and Kidney Transplantation for Polycystic Liver and Kidney-Renal Function and Outcome This suggests that in patients whose kidney function is already declining, performing both transplants at once may spare them a second major operation down the road. These are small cohorts, and every transplant center weighs the risks differently, but the overall message is that transplantation can be life-transforming for people whose quality of life has been destroyed by massive organ enlargement.
Diet, Water Intake, and Lifestyle Adjustments
For people with ADPKD specifically, there is growing interest in whether dietary changes can slow cyst growth by reducing levels of vasopressin, the hormone that drives fluid secretion into cysts. A pilot trial tested a combination of a low-sodium (1,500 mg per day), lower-protein diet along with adjusted water intake in 34 patients with ADPKD. The intervention group saw a significant drop in copeptin (a surrogate marker for vasopressin) and urine concentration compared to the control group.27American Journal of Kidney Diseases. Low-Osmolar Diet and Adjusted Water Intake for Vasopressin Reduction in Autosomal Dominant Polycystic Kidney Disease: A Pilot Randomized Controlled Trial The rationale is that vasopressin stimulates cyst growth, so keeping its levels low through hydration and diet could work in the same direction as tolvaptan, which blocks the vasopressin receptor directly. This was a small, short-term study, so it is too early to call dietary intervention a proven strategy, but it fits with the broader clinical advice to drink plenty of water throughout the day and limit salt intake.
Beyond diet, general recommendations for people with polycystic kidney disease include avoiding contact sports or activities with high risk of abdominal trauma (greatly enlarged kidneys are more vulnerable to injury), managing blood pressure aggressively, and avoiding nephrotoxic medications like nonsteroidal anti-inflammatory drugs when possible. For simple cysts that are not part of a genetic syndrome, no lifestyle changes are needed.
Family Planning and Genetic Testing
Because ADPKD is a dominant condition, every child of an affected parent has a 50% chance of inheriting the mutation. For couples who know they carry a PKD1 or PKD2 mutation, preimplantation genetic testing (PGT-M) during in vitro fertilization offers a way to select embryos that did not inherit the disease-causing variant before implantation.28Kidney International. Prenatal and preimplantation genetic testing for monogenic kidney disorders This technology has become increasingly popular among people with ADPKD, partly because the disease manifests later in life and the option of preventing it in the next generation is appealing even for people who are currently healthy. Customized PGT-M plans developed at fertility centers have been used successfully for several genetic kidney diseases beyond ADPKD as well.29Frontiers in Medicine. Combined Preimplantation Genetic Testing for Genetic Kidney Disease: Genetic Risk Identification, Assisted Reproductive Cycle, and Pregnancy Outcome Analysis
For ARPKD, which requires mutations in both copies of the PKHD1 gene, the situation is different. Both parents are carriers, and each pregnancy carries a 25% chance of an affected child. Because ARPKD can cause severe kidney and liver disease in infancy or childhood, prenatal genetic testing and carrier screening are important considerations for families with a known history. Genetic counseling can help families understand their specific risks and the full range of reproductive options available to them.
The Incidental Cyst Problem
One of the less obvious consequences of better and more frequent imaging is that doctors are finding cysts in people who were never looking for them. A scan ordered for back pain, a pre-surgical workup, or a cancer screening can reveal a cyst on the liver or kidney that was entirely unsuspected. In most cases this is medically meaningless, but it can trigger anxiety, additional imaging, and occasionally unnecessary procedures.
The challenge is distinguishing the vast majority of benign incidental cysts from the small number that warrant follow-up. For kidney cysts, the Bosniak system provides a clear framework: category I and II cysts can be forgotten, IIF cysts need surveillance imaging, and III and IV cysts need evaluation for possible malignancy.12PubMed. Bosniak Classification for Complex Renal Cysts Reevaluated: A Systematic Review For liver cysts, the approach is less standardized but follows similar logic: if the cyst meets strict criteria for a simple cyst on ultrasound, no follow-up is needed. If it does not, additional imaging with CT or MRI is warranted to rule out a cystic tumor or parasitic cyst.14PubMed Central. Evaluation of hepatic cystic lesions
If you have been told you have a cyst on your liver or kidney, the single most useful question to ask your doctor is whether it meets the criteria for a simple cyst. If it does, in the vast majority of cases you can put it out of your mind entirely. If it does not, the follow-up pathway is well-established, and doctors have good tools for distinguishing benign from concerning lesions without rushing to surgery.