Polycystic liver disease without autosomal dominant polycystic kidney disease

Polycystic liver disease is characterized by the presence of multiple bile duct-derived epithelial cysts scattered in the liver parenchyma. The natural history and clinical manifestations of polycystic liver disease are based on the disease as it manifests in patients with autosomal dominant polycystic kidney disease (ADPKD). The occurrence of polycystic liver disease independently from polycystic kidney disease has been known for a long time. More recently, a gene for autosomal dominant polycystic liver disease has been identified on chromosome 19p 13.2-13.1. Isolated polycystic liver disease is underdiagnosed and genetically distinct from polycystic liver disease associated with ADPKD but with similar pathogenesis and clinical manifestations. We report here two men with polycystic liver disease no associated with ADPKD. Ultrasound and computed tomography imaging were effective in documenting the underlying lesions non-invasively.     

Evaluation of hepatic cystic lesions

Hepatic cysts are increasingly found as a mere coincidence on abdominal imaging techniques, such as ultrasonography (USG), computed tomography (CT) and magnetic resonance imaging (MRI). These cysts often present a diagnostic challenge. Therefore, we performed a review of the recent literature and developed an evidence-based diagnostic algorithm to guide clinicians in characterising these lesions. Simple cysts are the most common cystic liver disease, and diagnosis is based on typical USG characteristics. Serodiagnostic tests and microbubble contrast-enhanced ultrasound (CEUS) are invaluable in differentiating complicated cysts, echinococcosis and cystadenoma/cystadenocarcinoma when USG, CT and MRI show ambiguous findings. Therefore, serodiagnostic tests and CEUS reduce the need for invasive procedures. Polycystic liver disease (PLD) is arbitrarily defined as the presence of > 20 liver cysts and can present as two distinct genetic disorders: autosomal dominant polycystic kidney disease (ADPKD) and autosomal dominant polycystic liver disease (PCLD). Although genetic testing for ADPKD and PCLD is possible, it is rarely performed because it does not affect the therapeutic management of PLD. USG screening of the liver and both kidneys combined with extensive family history taking are the cornerstone of diagnostic decision making in PLD. In conclusion, an amalgamation of these recent advances results in a diagnostic algorithm that facilitates evidence-based clinical decision making.     

Cardiovascular polycystins: insights from autosomal dominant polycystic kidney disease and transgenic animal models

Mutations in the PKD1 and PKD2 polycystin genes are responsible for autosomal dominant polycystic kidney disease (ADPKD), one of the most prevalent genetic kidney disorders. ADPKD is a multisystem disease characterized by the formation of numerous fluid-filled cysts in the kidneys, the pancreas, and the liver. Moreover, major cardiovascular manifestations are common complications in ADPKD. Intracranial aneurysms and arterial hypertension are among the leading causes of mortality in this disease. In the present review, we summarize our current understanding of the role of polycystins in the development, maintenance, and function of the cardiovascular system.     

Autosomal dominant polycystic liver disease in a family without polycystic kidney disease associated with a novel missense protein kinase C substrate 80K-H mutation

Polycystic liver disease (PLD) is characterized by the presence of multiple bile duct-derived epithelial cysts scattered in the liver parenchyma. PLD can manifest itself in patients with severe autosomal dominant polycystic kidney disease (ADPKD). Isolated autosomal dominant polycystic liver disease (ADPLD) is genetically distinct from PLD associated with ADPKD, although it may have similar pathogenesis and clinical manifestations. Recently, mutations in two causative genes for ADPLD, independently from ADPKD, have been identified. We report here a family (a mother and her daughter) with a severe form of ADPLD not associated with ADPKD produced by a novel missense protein kinase C substrate 80K-H (PRKCSH) mutation (R281W). This mutation causes a severe phenotype, since the two affected subjects manifested signs of portal hypertension. Doppler sonography, computed tomography (CT) and magnetic resonance (MR) imaging are effective in documenting the underlying lesions in a non-invasive way.     

Chronic pancreatitis with polycystic kidney disease: A rare coincidence?

IntroductionIn children, chronic pancreatitis (CP) is usually associated with anatomical anomalies of the pancreas and biliary tract or is genetically determined. Autosomal dominant polycystic kidney disease (ADPKD) may present with extrarenal cyst formation, sometimes involving the pancreas. Large enough, these cysts may cause pancreatitis in ADPKD patients.Case presentationHerein, we present a case of a 12-year-old Caucasian girl with recurrent pancreatitis with no identifiable traumatic, metabolic, infectious, drug, or immunologic causes. Structural anomalies of the pancreas, including cysts, were ruled out by imaging. However, bilateral cystic kidneys were found as an incidental finding. Her family history was negative for pancreatitis, but positive for polycystic kidney disease. Molecular analysis of ADPKD-causing mutations revealed a novel c.9659C>A (p.Ser3220*) mutation in the PKD1 gene confirming the clinical suspicion of ADPKD. Although CP may rarely occur as an extrarenal manifestation of ADPKD with pancreatic cysts, it is unusual in their absence. Thus, molecular analysis of pancreatitis susceptibility genes was performed and a homozygous pathologic c.180C>T (p.G60=) variant of the CTRC gene, known to increase the risk of CP, was confirmed.ConclusionThis is the first reported case of a pediatric patient with coincidence of genetically determined CP and ADPKD. Occurrence of pancreatitis in children with ADPKD without pancreatic cysts warrants further investigation of CP causing mutations.     

Chronic obstructive pancreatitis due to a pancreatic cyst in a patient with autosomal dominant polycystic kidney disease

Background—Autosomal dominant polycystic kidneydisease, the most frequent inherited polycystic disease, is a systemicdisorder characterised by the development of numerous and bilateralkidney cysts leading to chronic renal failure. Extrarenal cysts arelocated mainly in the liver but also in various organs including thepancreas. To our knowledge, complications of pancreatic cysts in thisdisease have never been reported.
Patient—The first case of painful chronicobstructive pancreatitis due to a true pancreatic cyst in a patientwith autosomal dominant polycystic kidney disease is reported.Abdominal transparietal and endoscopic ultrasonography, computedtomography, and endoscopic retrograde cholangiopancreatography showed acystic lesion in the body of the pancreas associated with upstreamdilatation of the main pancreatic duct. Intraoperative ultrasonographybefore and after cyst fluid aspiration, and pancreatography andpathological examination of the resected distal pancreas confirmed thatboth main pancreatic duct enlargement and chronic pancreatitis were caused by a benign cyst.
Conclusion—Chronic obstructive pancreatitisshould be added to the extrarenal complications of autosomal dominantpolycystic kidney disease.

Keywords:chronic obstructive pancreatitis; pancreatic cyst; autosomal dominant polycystic kidney disease; distal pancreatectomy

     

Seminal vesicle cysts and infertility in autosomal dominant polycystic kidney disease

Autosomal dominant polycystic kidney disease (ADPKD) is a systemic hereditary disorder characterized by bilateral diffuse renal cysts. Extrarenal involvement is a well known manifestation of ADPKD. Cysts in the liver, pancreas, lung, spleen, oesophagus, ovary, testis, epididymis, prostate, thyroid, bladder, uterus, brain, paraespinal, and seminal vesicle have also been described. The occurrence of seminal vesicle cysts is often unrecognised. We report here a man with seminal vesicle cysts and azoospermia associated with ADPKD. Seminal vesicle cysts are not uncommon in ADPKD and in some cases it is associated with infertility. Ultrasound and computed tomography imaging were effective in documenting the underlying lesions non-invasively. Studies evaluating fertility in patients with seminal vesicle cysts and ADPKD are needed.     

Isolated polycystic liver disease as a distinct genetic disease,unlinked to polycystic kidney disease 1 and polycystic kidney disease 2

Polycystic liver disease (PLD) is proven to occur either sporadically or in association with autosomal dominant polycystic kidney disease (ADPKD), whereas the existence of an isolated (i.e., without any kidney cyst) familial form is disputed. We describe a family with definitely isolated PLD transmitted through three generations and exclude the linkage of the disease to the genetic markers of PKD1 and PKD2, the two main loci responsible for ADPKD. These findings strongly support the existence of PLD as a genetic disease distinct from the known forms of ADPKD. (Hepatology 1996 Feb;23(2):249-52)     

Zystische Nierenerkrankungen im Kindesalter

Hereditary cystic kidney diseases are a clinically and genetically heterogeneous group of diseases usually manifesting in utero and/or during the neonatal period. However, these disorders might remain clinically silent until adulthood. Most, if not all, hereditary cystic kidney diseases are due to mutations in proteins, which are localized in primary cilia, basal bodies and centrosomes. This led to the new entity of “ciliopathies”. Since cilia perform diverse biological roles and are present in several other organs like liver, bile duct, eyes, brain, pancreas and others, this explains both the multiple organ involvement and the considerable phenotypical overlap between the different hereditary cystic kidney diseases. A brief review is given of the clinical presentation and differential diagnosis of hereditary cystic kidney diseases with special emphasis on differentiation from autosomal dominant polycystic kidney disease (ADPKD) as well as new therapeutic options especially in autosomal recessive polycystic kidney disease (ARPKD).     

Recurrent pancreatitis in a patient with autosomal-dominant polycystic kidney disease.

Autosomal-dominant polycystic kidney disease is an inherited disorder characterized by multiple cysts in kidneys and other organs. A 63-year-old man was evaluated for the etiology of recurrent pancreatitis and chronic renal failure. Multiple cysts of kidneys, liver, and pancreas and pancreas divisum was diagnosed. Pancreatitis should be included in the differential diagnosis of abdominal pain in patients with ADPKD. Pancreas divisum may be a predisposing factor for acute pancreatitis in these patients.     

A case of successful management of portosystemic shunt with autosomal dominant polycystic kidney disease by balloon-occluded retrograde transvenous obliteration and partial splenic embolization

We describe a patient with autosomal dominant polycystic kidney disease who was successfully managed for severe abdominal distension, impaired liver function and a portosystemic shunt by interventional therapies. The patient's intra-hepatic portal vein was compressed and narrowed by multiple liver cysts, which resulted in a decrease of the portal blood flow and portal hypertension due to a huge gastro-renal shunt These haemodynamic changes were assumed to contribute to insufficient protein synthesis in the liver. Therefore, we first repeatedly performed minocycline hydrochloride instillations to treat the multiple liver cysts. Then, we conducted a partial splenic embolization to prevent elevation of the portal vein pressure prior to balloon-occluded retrograde transvenous obliteration which was performed to increase the portal blood flow. The portal blood flow markedly increased, and protein synthesis in the liver also recovered and the clinical symptoms improved. The patient has been monitored for more than two years up to the present and her liver function parameters have remained within the normal range. Renal insufficiency is known to be a major prognostic factor in autosomal dominant polycystic kidney disease. In some cases, however, liver involvement with multiple cysts may result in a fatal outcome. In such cases, interventional therapies, as provided to this patient, should be considered.     

Surgical management of polycystic liver disease

Adult polycystic liver disease (PCLD) is an autosomal dominant condition commonly associated with autosomal dominant polycystic kidney disease (ADPKD). However in the last decade, it has been recognized that there is a distinct form of autosomal dominant PCLD that arises without concomitant ADPKD. Early knowledge of the pathogenesis was gained from the study of hepatic cysts in patients with ADPKD. Bile duct overgrowth after embryogenesis results in cystic hepatic dilatations that are known as biliary microhamartomas or von Meyenburg complexes. Further dilatation arises from cellular proliferation and fluid secretion into these cysts. There is a variable, broad spectrum of manifestations of PCLD. Although PCLD is most often asymptomatic, massive hepatomegaly can lead to disabling symptoms of abdominal pain, early satiety, persistent nausea, dyspnea, ascites, biliary obstruction, and lower body edema. Complications of PCLD include cyst rupture and cyst infection. Also, there are associated medical problems, especially intracranial aneurysms and valvular heart disease, which clinicians need to be aware of and evaluate in patients with PCLD. In asymptomatic patients, no treatment is indicated for PCLD. In the symptomatic patient, surgical therapy is the mainstay of treatment tailored to the extent of disease for each patient. Management options include cyst aspiration and sclerosis, open or laparoscopic fenestration, liver resection with fenestration, and liver transplantation. The surgical literature discussing treatment of PCLD, including techniques, outcomes, and complication rates, are summarized in this review.     

Prevalence of Cysts in Seminal Tract and Abnormal Semen Parameters in Patients with Autosomal Dominant Polycystic Kidney Disease

Background and objectives: Autosomal dominant polycystic kidney disease is a systemic disorder with a wide range of extrarenal involvement. The scope of this study was to analyze the prevalence of seminal cysts and to correlate these findings with the sperm parameters in patients with autosomal dominant polycystic kidney disease.Design, setting, participants, & measurements: A prospective study enrolled 30 adult men with autosomal dominant polycystic kidney disease. Of these 30 patients, 22 agreed to provide a semen sample for analysis, and 28 of 30 agreed to undergo an ultrasound rectal examination. Data obtained from the semen tests and from the ultrasound study were compared.Results: Cysts in the seminal tract were present in 10 (43.47%) of 28 individuals. Twenty of 22 patients showed abnormal semen parameters, with asthenozoospermia as the most common finding. No correlation between ultrasound findings and sperm abnormalities was observed.Conclusions: The presence of cysts in the seminal tract is remarkably high (43.47%); however, this finding does not correlate with sperm abnormalities, which are also a frequent finding, especially asthenozoospermia. This semen abnormality is probably related to the abnormal function of polycystins. More attention should be paid to reproductive aspects in the initial evaluation of patients with autosomal dominant polycystic kidney disease before their ability to conceive is further impaired by uremia.Autosomal dominant polycystic kidney disease (ADPKD) is one of the most common inherited disorders, occurring in approximately one of 1000 individuals in the general population. ADPKD is a genetically heterogeneous disorder caused by mutations in either the PKD1 or the PKD2 gene, which encode for the proteins polycystin-1 and polycystin-2, respectively. Most ADPKD cases (>80%) are due to mutations of the PKD1 gene and are associated with an earlier onset and faster disease progression than the PKD2 phenotype. ADPKD has been widely studied during the past decade, having shed new light on polycystin structure and function. Polycystin-1 and -2 are highly conserved ubiquitous transmembrane proteins that, in the kidney, are located in epithelial cells of renal tubules, in particular in the primary cilia at the luminal side of the tubules, as well as in other areas of the renal cell epithelium. Polycystin-1 is a large protein with a long extracellular N-terminal region, 11 transmembrane domains, and a short intracellular C-terminal tail. Polycystin-2 is structurally related to the transient receptor potential channel family, and it is known to function as a nonselective cation channel permeable to Ca². Polycystin-1 and -2 form heteromeric complexes and co-localize in the primary cilium of renal epithelial cells. The primary cilium is a long nonmotile tubular structure located in the apical surface of epithelial cells in renal tubules. Its function was unknown for a long time; however, recent studies proposed a role of the primary cilium as a mechanoreceptor that may sense changes in apical fluid flow and may be able to transduce them into an intracellular Ca²⁺ signaling response (1). This model involves the participation of polycystin-1 as a mechanical sensor of ciliary bending induced by luminal fluid flow. Bending of the cilium would cause a conformational change in polycystin-1 that would in turn activate polycystin-2–associated Ca²⁺ channel, increasing the intracellular Ca²⁺ concentration and triggering intracellular signaling pathways leading to normal kidney development.Many extrarenal features are well known in ADPKD. Hepatic cysts are the most common extrarenal manifestation of ADPKD. More than 75% of individuals who have ADPKD and are older than 60 yr have hepatic cysts (2). The prevalence of intracranial aneurysms is approximately 10%, and the prevalence of pancreatic cysts is 6 to 9%; however, other extrarenal organ involvement, such as aortic abdominal aneurysms, colonic diverticulae, and cardiac valve abnormalities, has been questioned for ADPKD. Other rare associations have been reported, but their prevalence remains unknown. This could be the case for thoracic aortic aneurysm, hernias, and seminal tract cysts.There have been several case reports on cysts in epididymis, seminal vesicles, prostate, and testes in patients with ADPKD. Also some cases of infertility have been reported. Even a structural abnormality in the sperm from some patients with ADPKD has been reported; however, ADPKD is not a disease that is considered to cause infertility. Fewer than 10% of cases are sporadic, and in the remaining 90%, the disease has been inherited independently from the mother or the father. Moreover, large pedigrees are frequent. The aim of this study was to determine the prevalence of cysts in the seminal tract and to correlate it with sperm parameters.     

Acute abdomen and ascites as presenting features of autosomal dominant polycystic kidney disease

We describe a patient with sudden onset of abdominal pain and ascites,leading to the diagnosis of autosomal dominant polycystic kidney disease(ADPKD).Her presentation was consistent with acute liver cyst rupture as the cause of her acute illness.A review of literature on polycystic liver disease in patients with ADPKD and current management strategies are presented.This case alerts physicians that ADPKD could occasionally present as an acute abdomen;cyst rupture related to ADPKD may be considered in the differential diagnoses of acute abdomen.     

Secretion of cytokines and growth factors into autosomal dominant polycystic kidney disease liver cyst fluid

The principal extrarenal manifestation of autosomal dominant polycystic kidney disease (ADPKD) involves formation of liver cysts derived from intrahepatic bile ducts. Autocrine and paracrine factors secreted into the cyst would be positioned to modulate the rate of hepatic cyst growth. The aim of this study was to identify potential growth factors present in human ADPKD liver cyst fluid. Cytokine array and enzyme-linked immunosorbent assay analysis of human ADPKD liver cyst fluid detected epithelial neutrophil attractant 78, interleukin (IL)-6 (503 +/- 121 pg/mL); and IL-8 (4,488 +/- 355 pg/mL); and elevated levels of vascular endothelial growth factor compared with non-ADPKD bile (849 +/- 144 pg/mL vs. 270 pg/mL maximum concentration). ADPKD liver cyst cell cultures also released IL-8 and vascular endothelial growth factor, suggesting that cystic epithelial cells themselves are capable of secreting these factors. Western blotting of cultured cyst cells and immunostaining of intact cysts demonstrate that cysteine-X-cysteine receptor 2, an epithelial neutrophil attractant 78 and IL-8 receptor, is expressed at the apical domain of cyst lining epithelial cells. Suggesting the cystic epithelial cells may exist in hypoxic conditions, electron microscopy of the ADPKD liver cyst epithelium revealed morphological features similar to those observed in ischemic bile ducts. These features include elongation, altered structure, and diminished abundance of apical microvilli. In conclusion, IL-8, epithelial neutrophil attractant 78, IL-6, and vascular endothelial growth factor may serve as autocrine and paracrine factors to direct errant growth of ADPKD liver cyst epithelia. Interruption of these signaling pathways may provide therapeutic targets for inhibiting liver cyst expansion.     

Autosomal dominant polycystic kidney disease is associated with an increased prevalence of radiographic bronchiectasis

BACKGROUND: Autosomal dominant polycystic kidney disease (ADPKD) is a common disease with several known extrarenal manifestations, although no known pulmonary features. The formation of renal cysts in ADPKD has been attributed to dysfunction of primary cilia and the primary cilia-related proteins polycystin-1 (in 85% of cases) and polycystin-2 in renal epithelial cells. The goals of this study were to characterize the normal expression of polycystin-1 in the motile cilia of airway epithelial cells and to evaluate lung structure in ADPKD patients. METHODS: Airway epithelium from non-ADPKD patients was immunostained to localize polycystin-1 expression, and lung tissue from ADPKD patients was examined for pathologic changes. CT scans from ADPKD patients (n = 95) and a control group of non-ADPKD chronic kidney disease patients (n = 95) were retrospectively reviewed for the presence of bronchiectasis using defined criteria. RESULTS: Immunostaining revealed polycystin-1 expression in the motile cilia of non-ADPKD airway epithelial cells. Lung tissue from one of five available ADPKD patient autopsies revealed histologic changes of bronchiectasis. Review of CT scans revealed a threefold-increased prevalence of bronchiectasis in the ADPKD group compared to the control group (37% vs 13%, p = 0.002). CONCLUSIONS: ADPKD patients demonstrate an increased prevalence of radiographic bronchiectasis, a previously unrecognized manifestation of the disease. This association suggests that patients with primary cilia-associated diseases may be at risk for airway disease.     

Pancreatic involvement in von Hippel-Lindau disease: report of two cases and review of the literature

BACKGROUND: Von Hippel-Lindau (VHL) disease is an autosomal dominant multicancer syndrome caused by the germline mutation of a tumor suppressor gene. Affected individuals develop benign and malignant tumors of the central nervous system, kidneys, adrenal glands, pancreas, and reproductive system. Although VHL disease is mainly diagnosed after the detection of central nervous system tumors, they may not always be the first presentation. CASE REPORT: We report the case of a patient presenting with pancreatic cysts for whom the final genetic diagnosis of VHL disease was formulated. During management, the use of endoscopic ultrasonography (EUS) proved to be valid in the characterization of the pancreatic lesions. Family screening also revealed the genetic mutation in the patient's son and imaging investigations showed the presence of multiple tumors. The diagnosis allowed us to plan appropriate follow-up for both, thus improving their life expectancy. CONCLUSIONS: Gastroenterologists should be aware of the frequent pancreatic involvement in VHL disease and EUS can be useful in this setting.     

Cyst Infections in Patients with Autosomal Dominant Polycystic Kidney Disease

Background and objectives: Cyst infection is a complex diagnostic and therapeutic issue in patients with autosomal dominant polycystic kidney disease (ADPKD); however, published data regarding the diagnosis and the management of cyst infections in patients with ADPKD are sparse.Design, setting, participants, & measurements: A retrospective study was conducted in a referral center for patients with ADPKD in Paris, France. We identified using a computerized database all patients who had ADPKD and were admitted in the nephrology department of Hôpital Necker between January 1998 and August 2008 with likely or definite renal and/or hepatic cyst infection. Medical files of all included patients were reviewed.Results: Among 389 identified patients with ADPKD, 33 (8.4%) had 41 episodes of cyst infection, including eight definite and 33 likely cases. The incidence of cyst infections in patients with ADPKD was 0.01 episode per patient per year. Microbiological documentation was available for 31 episodes (75%), Escherichia coli accounting for 74% of all retrieved bacterial strains. Positron emission tomography scan proved superior to ultrasound, Computed tomography scan, and magnetic resonance imaging for the detection of infected cysts. Clinical efficacy of initial antibiotic treatment was noted in 71% of episodes. Antibiotic treatment modification was more frequently required for patients who were receiving initial monotherapy compared with those who were receiving bitherapy. Large (diameter >5 cm) infected cysts frequently required drainage.Conclusions: Positron emission tomography scan will probably make the diagnosis of cyst infections easier and more accurate. Antibiotic association, including a fluoroquinolone, and the drainage of large infected cysts remain the main treatment for cyst infections.Autosomal dominant polycystic kidney disease (ADPKD) represents the most common inherited disorder affecting one in 500 to one in 1000 live births and accounting for 4 to 10% of dialysis patients. The most striking feature of ADPKD is the occurrence of numerous renal and hepatic cysts, which arise from various renal tubule segments and lead to an increased kidney size. Cysts are also associated with some of the most common complications of ADPKD: Intracystic bleeding, gross hematuria, obstruction mainly caused by liver cysts, and, most important, infections. Kidney and liver cyst infection is a complex diagnostic and therapeutic challenge; however, the literature on the diagnosis and the management of urinary tract infections and particularly cyst infections in patients with ADPKD is relatively sparse. The clinical, microbiological, and radiologic features of cyst infections as well as treatment regimens remain ill-defined (1–3). We conducted a retrospective, single-center study to assess the clinical and radiologic presentation and treatment outcomes of cyst infections in patients with ADPKD.     

Autosomal Dominant Polycystic Kidney Disease in which the Polycystic Liver Volume Was Reduced by Rigorous Blood Pressure Control

Polycystic liver disease (PLD) is the most common extrarenal manifestation of autosomal dominant polycystic kidney disease (ADPKD). However, current treatments for PLD are only supportive. We experienced a case of enlarged kidneys and liver in a 53-year-old Japanese man with ADPKD who was on hemodialysis. He underwent renal transcatheter arterial embolization (TAE) for enlarged kidneys. His blood pressure (BP) decreased after renal TAE, and his liver volume decreased from 5,259 mL to 4,647 mL (11.6% reduction) within 1 year after renal TAE. This case suggests that rigorous blood pressure control may be beneficial for ameliorating enlarged PLD.     

Cardiovascular, skeletal, and renal defects in mice with a targeted disruption of the Pkd1 gene

Autosomal dominant polycystic kidney disease (ADPKD) is characterized by cyst formation in the kidney, liver, and pancreas and is associated often with cardiovascular abnormalities such as hypertension, mitral valve prolapse, and intracranial aneurysms. It is caused by mutations in PKD1 or PKD2, encoding polycystin-1 and -2, which together form a cell surface nonselective cation ion channel. Pkd2-/- mice have cysts in the kidney and pancreas and defects in cardiac septation, whereas Pkd1(del34) -/- and Pkd1(L) -/- mice have cysts but no cardiac abnormalities, although vascular fragility was reported in the latter. Here we describe mice carrying a targeted mutation in Pkd1 (Pkd1(del17-21betageo)), which defines its expression pattern by using a lacZ reporter gene and may identify novel functions for polycystin-1. Although Pkd1(del17-21betageo) +/- adult mice develop renal and hepatic cysts, Pkd1(del17-21betageo) -/- embryos die at embryonic days 13.5-14.5 from a primary cardiovascular defect that includes double outflow right ventricle, disorganized myocardium, and abnormal atrio-ventricular septation. Skeletal development is also severely compromised. These abnormalities correlate with the major sites of Pkd1 expression. During nephrogenesis, Pkd1 is expressed in maturing tubular epithelial cells from embryonic day 15.5. This expression coincides with the onset of cyst formation in Pkd1(del34) -/-, Pkd1(L) -/-, and Pkd2-/- mice, supporting the hypothesis that polycystin-1 and polycystin-2 interact in vivo and that their failure to do so leads to abnormalities in tubule morphology and function.