Gastric duplication cyst masquerading as a mucinous pancreatic cyst: case report and literature review.

Gastric duplication cysts are rare cystic neoplasms that are often difficult to distinguish from other entities. We describe a healthy 44-year-old woman who presented with acute right lower quadrant abdominal and flank pain as well as chronic nausea and constipation. Her physical examination was unremarkable but contrasted computed tomography revealed a 6 cm cystic lesion between the stomach and body of the pancreas. Endoscopic ultrasonography and fluid analysis were consistent with a mucinous cyst with a markedly elevated fluid carcinoembryonic antigen level. The patient subsequently underwent a laparoscopic distal pancreatectomy, which was converted to an open procedure when the lesion was noted to be adherent to the coeliac axis. Intraoperative endoscopy revealed no abnormality. Final pathology revealed a gastric duplication cyst. The patient recovered well and was asymptomatic on follow-up. In this report, we discuss the incidence, natural history and management of this rare entity.

Survival Benefit of Adjuvant Radiation Therapy for Gastric Cancer following Gastrectomy and Extended Lymphadenectomy.

Purpose. Although randomized trials suggest a survival benefit of adjuvant chemotherapy and radiation therapy (XRT) for gastric adenocarcinoma, its use in patients who undergo an extended lymphadenectomy is less clear. The purpose of this study was to determine if a survival benefit exists in gastric cancer patients who receive adjuvant XRT following resection with extended lymphadenectomy. Methods. The SEER registry was queried for records of patients with resected gastric adenocarcinoma from 1988 to 2007. Multivariable Cox regression models were used to assess independent prognostic factors affecting overall survival (OS) and disease-specific survival (DSS). Results. Of 15,060 patients identified, 3,208 (21%) received adjuvant XRT. Adjuvant XRT was independently associated with improved OS (HR 0.67, CI 0.64-0.71) and DSS (HR 0.69, CI 0.65-0.73) in stages IB through IV (M0). This OS and DSS benefit persisted regardless of the extent of lymphadenectomy. Furthermore, lymphadenectomy with >25 LN resected was associated with improved OS and DSS compared with <15 LN or 15-25 LN. Conclusion. This population-based study shows a survival benefit of adjuvant XRT following gastrectomy that persists in patients who have an extended lymphadenectomy. Furthermore, removal of >25 LNs results in improved OS and DSS compared with patients who have fewer LNs resected.

Risk of malignancy in resected cystic tumors of the pancreas < or =3 cm in size: is it safe to observe asymptomatic patients? A multi-institutional report.

Recent international consensus guidelines propose that cystic pancreatic tumors less than 3 cm in size in asymptomatic patients with no radiographic features concerning for malignancy are safe to observe; however, there is little published data to support this recommendation. The purpose of this study was to determine the prevalence of malignancy in this group of patients using pancreatic resection databases from five high-volume pancreatic centers to assess the appropriateness of these guidelines. All pancreatic resections performed for cystic neoplasms < or =3 cm in size were evaluated over the time period of 1998-2006. One hundred sixty-six cases were identified, and the clinical, radiographic, and pathological data were reviewed. The correlation with age, gender, and symptoms (abdominal pain, nausea and vomiting, jaundice, presence of pancreatitis, unexplained weight loss, and anorexia), radiographic features suggestive of malignancy by either computed tomography, magnetic resonance imaging, or endoscopic ultrasound (presence of solid component, lymphadenopathy, or dilated main pancreatic duct or common bile duct), and the presence of malignancy was assessed using univariate and multivariate analysis. Among the 166 pancreatic resections for cystic pancreatic tumors < or =3 cm, 135 cases were benign [38 serous cystadenomas, 35 mucinous cystic neoplasms, 60 intraductal papillary mucinous neoplasms (IPMN), 1 cystic papillary tumor, and 1 cystic islet cell tumor], whereas 31 cases were malignant (14 mucinous cystic adenocarcinomas and 13 invasive carcinomas and 4 in situ carcinomas arising in the setting of IPMN). A greater incidence of cystic neoplasms was seen in female patients (99/166, 60%). Gender was a predictor of malignant pathology, with male patients having a higher incidence of malignancy (19/67, 28%) compared to female patients (12/99, 12%; p < 0.02). Older age was associated with malignancy (mean age 67 years in patients with malignant disease vs 62 years in patients with benign lesions (p < 0.05). A majority of the patients with malignancy were symptomatic (28/31, 90%). Symptoms that correlated with malignancy included jaundice (p < 0.001), weight loss (p < 0.003), and anorexia (p < 0.05). Radiographic features that correlated with malignancy were presence of a solid component (p < 0.0001), main pancreatic duct dilation (p = 0.002), common bile duct dilation (p < 0.001), and lymphadenopathy (p < 0.002). Twenty-seven of 31(87%) patients with malignant lesions had at least one radiographic feature concerning for malignancy. Forty-five patients (27%) were identified as having asymptomatic cystic neoplasms. All but three (6.6%) of the patients in this group had benign disease. Of the patients that had no symptoms and no radiographic features, 1 out of 30 (3.3%) had malignancy (carcinoma in situ arising in a side branch IPMN). Malignancy in cystic neoplasms < or =3 cm in size was associated with older age, male gender, presence of symptoms (jaundice, weight loss, and anorexia), and presence of concerning radiographic features (solid component, main pancreatic duct dilation, common bile duct dilation, and lymphadenopathy). Among asymptomatic patients that displayed no discernable radiographic features suggestive of malignancy who underwent resection, the incidence of occult malignancy was 3.3%. This study suggests that a group of patients with small cystic pancreatic neoplasms who have low risk of malignancy can be identified, and selective resection of these lesions may be appropriate.

Surgical management of intra-abdominal desmoid tumours.

BACKGROUND: Intra-abdominal desmoids are uncommon neoplasms. The aggressive nature of these tumours and the potential for major morbidity secondary to resection can present a difficult surgical dilemma. METHODS: Patients with histologically confirmed intra-abdominal desmoid tumours undergoing laparotomy were identified from a prospective database. Clinical features and outcomes in this group were evaluated. RESULTS: The study group comprised 24 patients. Sixteen patients underwent complete resection of the tumour while eight had biopsy only, with or without intestinal bypass. Small intestinal resection was performed in 12 patients, including three who had a near-total enterectomy. Median follow-up was 62 months, with an actuarial overall survival rate of 73 per cent at 10 years. There was no difference in survival rate between completely resected and unresected patients (P = 0.73). There were seven deaths in the entire group, of which four were in those undergoing complete resection. CONCLUSION: Operation can cure patients with intra-abdominal desmoid tumours, but may result in significant morbidity, especially from loss of small intestine. No other therapy is a predictably good alternative to operation but the natural history of desmoids is often characterized by prolonged periods of stability or even regression. A period of watchful waiting, until significant symptoms develop, may be the most appropriate course in patients who risk mesenteric vascular injury or substantial enterectomy with attempts at resection.

Hepatic resection using intermittent vascular inflow occlusion and low central venous pressure anesthesia improves morbidity and mortality.

Hepatic resection results in significant morbidity and mortality primarily related to intraoperative blood loss. Intermittent vascular inflow occlusion (VO) and low central venous pressure (CVP) during hepatectomy have been used to reduce blood loss. To determine the benefit of VO and low CVP, we reviewed the outcomes of 168 consecutive patients who underwent liver resection. The results of 78 patients who had undergone hepatic resection between 1993 and 1998 with the use of VO and low CVP (post-VO/CVP) were compared to the previous 90 patients who had undergone hepatectomy without VO and low CVP (pre-VO/CVP) between 1979 and 1992. Hepatectomies were performed for metastatic disease (65%), hepatoma (20%), and benign tumors (15%). Resections included 18 trisegmentectomies, 67 lobectomies, and 83 segmental resections. Patients in both groups were similar with regard to extent of resection. Post-VO/CVP patients had significantly lower median estimated blood loss (725 ml vs. 2300 ml, P <0.001), less postoperative morbidity (10.3% vs. 22. 2%, P = 0.038), lower in-hospital mortality (2.6% vs. 10%, P = 0. 050), fewer days in the intensive care unit (1.6 +/- 0.1 days vs. 5. 6 +/- 1.2 days, P = 0.003), and shorter overall length of stay (8.0 +/- 0.5 days vs. 15.0 +/- 1.6 days, P <0.001) than pre-VO/CVP patients. These data suggest that VO and low CVP during liver resection may improve patient outcomes.

T3N0 rectal cancer: results following sharp mesorectal excision and no adjuvant therapy.

Adjuvant chemoradiation therapy following resection of T3N0 rectal cancer is recommended in order to reduce the incidence of local recurrence and improve survival. However, recent experience with rectal cancer resection utilizing sharp dissection and total mesorectal excision has resulted in a reduction in local recurrence rates to as low as 5% without adjuvant treatment. The purpose of this study was to determine if rectal cancer resection utilizing sharp mesorectal excision alone is adequate treatment for local control of T3N0 rectal cancer. Between July 1986 and December 1993, 95 patients with T3N0M0 rectal cancer underwent resection with sharp mesorectal excision and did not receive any adjuvant therapy. Various prognostic factors were analyzed for their association with local recurrence and survival. Seventy-nine patients had a low anterior resection, 10 of whom had a coloanal anastomosis, and 16 had an abdominoperineal resection. The median follow-up was 53.3 months. Six patients had local recurrence, 12 had distant recurrence, and three had local and distant recurrences. The overall local recurrence rate was 9% crude and 12% 5-year actuarial. The overall crude recurrence rate was 22%. The 5-year disease-specific survival rate was 86.6% with an overall survival of 75%. Postoperative complications occurred in 18 patients (19%). Five patients (6%) had a documented anastomotic leak. Perioperative mortality was 3%. No technical factors, including type of resection (low anterior vs. abdominoperineal), location of tumor, or extent of resection margin, were significant for determining local recurrence. The only histopathologic marker significant for determining local recurrence was lymphatic invasion (P <0.04). Sharp mesorectal excision with low anterior resection or abdominoperineal resection for T3N0M0 rectal cancer results in a local recurrence rate of less than 10% without the use of adjuvant therapy. Therefore, in select patients with T3N0M0 rectal cancer, the standard use of adjuvant therapy for local control may not be justified.

Extremity and trunk desmoid tumors: a multifactorial analysis of outcome.

BACKGROUND: The natural history of desmoid tumors remains an enigma. Previous reports attempting to identify their biology have included recurrent and primary tumors as well as tumors from both intra- and extra-abdominal sites. The purpose of this study was to analyze patients with primary extremity and trunk desmoid tumors treated and followed at a single institution and to determine factors influencing disease free survival. METHODS: Between July 1982 and June 1997, 189 patients with extremity and superficial trunk desmoid tumors were treated and followed prospectively. Of these, 105 presented with primary disease and formed the basis of this study. RESULTS: The median follow-up for the entire group of patients was 49 months; it was 46 months for patients who did not develop a local recurrence. During this time, 24 patients (23%) had a local recurrence. No patients died of disease. The 2-year and 5-year local recurrence free survival rates were 80% and 75%, respectively. None of the prognostic factors analyzed, including age, gender, depth of tumor, size of tumor, or tumor site, were significant for predicting local recurrence. Moreover, positive resection margins were not predictive of recurrence. The selective use of adjuvant radiation therapy did not influence the rate of local recurrence regardless of the margin status. CONCLUSIONS: Attempts to achieve negative resection margins may result in unnecessary morbidity and may not prevent local recurrence. Operations that preserve function and structure should be the primary goal, because the presence of residual disease cannot be clearly shown to impact adversely on 5-year disease free or overall survival.

Positive peritoneal cytology predicts unresectability of pancreatic adenocarcinoma.

BACKGROUND: Peritoneal cytology is clinically useful in gastric and gynecologic malignancies. Its role in pancreatic adenocarcinoma remains less well defined. Controversy exists as to the relationship between percutaneous fine needle aspiration (FNA) of the pancreas and shedding of malignant cells with the peritoneum. The aim of this study was to determine whether positive peritoneal cytology (PPC) predicts unresectability of pancreatic adenocarcinoma and impacts on overall survival. In addition, the study aimed to determine whether antecedent FNA increases the incidence of PPC. STUDY DESIGN: Between January 1993 and June 1996, 228 patients with radiographically resectable pancreatic adenocarcinoma underwent laparoscopic staging. Specimens were taken from right and left upper quadrants at the beginning of laparoscopy. Various prognostic factors were analyzed. RESULTS: PPC was identified in 34 patients (15%). Of patients that had an antecedent FNA, 20% had PPC, and 13% of those without an antecedent FNA had PPC (p = 0.22). The majority of patients with PPC had stage IV disease (26 of 34 [76%]) and only 8 (24%) had no evidence of metastases. Overall survival was significantly higher in patients with negative peritoneal cytology (NPC) compared with PPC (p<0.0006). PPC had a positive predictive value of 94.1%, specificity of 98.1%, and a sensitivity of 25.6% for determining unresectability of pancreatic adenocarcinoma. PPC was not an independent prognostic variable for survival on multivariate analysis. CONCLUSIONS: PPC is associated with advanced disease and is highly specific in predicting unresectability of pancreatic adenocarcinoma, resulting in decreased survival. Antecedent FNA is not associated with an increased the incidence of PPC, nor does it significantly impact on overall survival.

Laparoscopic evaluation in pancreatic cancer.

Pancreatic cancer continues to carry a poor overall prognosis. The majority of patients have advanced disease at the time of presentation. Dynamic, contrast-enhanced computed tomography (CT) has become the radiographic study of choice in the pre-operative staging of patients with pancreatic cancer. While it has been shown to be highly sensitive in determining unresectability of peri-ampullary tumors, the ability of CT to predict accurately which tumors can be safely resected is still limited. Laparoscopic staging of peri-ampullary tumors is superior to dynamic CT in visualizing small liver and peritoneal metastases. The addition of laparoscopic ultrasound during laparoscopic staging enhances the ability of laparoscopy to determine resectability of these tumors and approaches the accuracy of open exploration without increasing significant morbidity or mortality. Patients who are deemed unresectable at the time of laparoscopy can undergo palliative biliary and/or gastric bypass procedures laparoscopically and further minimize the morbidity of laparotomy.

Open-chest cardiac massage without major thoracotomy: metabolic indicators of coronary and cerebral perfusion.

OBJECTIVE: To compare the coronary and cerebral perfusion achieved using a novel method of minimally-invasive, direct cardiac massage to that obtained using bimanual, open-chest cardiac massage. DESIGN: Prospective, controlled animal study with repeated measures. SETTING: University research laboratory. SUBJECTS: Large domestic swine. INTERVENTIONS: Aortic, coronary sinus, jugular venous and pulmonary artery catheters were placed. Following an equilibration period, ventricular fibrillation was induced. After 4 min of untreated ventricular fibrillation, animals underwent bimanual, open-chest cardiac massage (N = 6) or minimally-invasive, direct cardiac massage using a novel device for direct cardiac compression (N = 6). Adrenaline was administered at a dose of 1 mg intravenously every 5 min. MEASUREMENTS: Systemic metabolic parameters, (arterial PO2, PCO2 and lactate concentration) and coronary sinus and jugular venous metabolic parameters (pH, PVO2, SVO2, PVCO2 and lactate concentration) were measured and calculated (coronary sinus/jugular-arterial SVO2, coronary sinus/jugular-arterial PCO2 and lactate differences) at baseline and at 10, 20 and 30 min following induction of ventricular fibrillation. Animals were euthanised after 30 min with no attempt at defibrillation. MAIN RESULTS: Oxygen tension and oxygen saturation of coronary sinus blood declined significantly during the experimental period, but no differences were noted between treatment groups. The coronary sinus-arterial oxygen saturation difference increased during the study with no significant differences between groups. Coronary sinus PCO2 and the coronary sinus-arterial PCO2 difference increased significantly in both experimental groups during cardiac massage. No inter-group differences were noted. A similar relationship was noted in coronary sinus lactate values. The coronary sinus-arterial lactate difference displayed a positive balance at all intervals with no differences noted between group values. The oxygen tension and oxygen saturation of jugular venous blood, were reduced from baseline levels with both treatments. The jugular-arterial oxygen saturation difference increased in both groups compared to baseline values. Between group values were significantly different only at the 20 min interval. Both the jugular venous PCO2 and the jugular-arterial PCO2 gradient were elevated at all intervals, but no inter-group differences were noted. Jugular venous lactate concentration rose steadily with time in both groups. No significant increase in the jugular-arterial lactate gradient was noted at any time point. CONCLUSIONS: Minimally-invasive, direct cardiac massage provides coronary and cerebral perfusion similar to that achieved using standard open-chest cardiac massage. This method may provide a more effective substitute for standard, closed-chest cardiac massage in cases of refractory cardiac arrest.

Isoproterenol-induced gastric mucosal protection from bile acid. Role of endogenous prostaglandins.

Topical isoproterenol is a potent protective agent against bile acid-induced gastric mucosal injury in hypotensive and normotensive rats. This study was undertaken to ascertain what role endogenous prostaglandins and gastric mucosal blood flow play in isoproterenol-induced protection. Accordingly, anesthetized, fasted rats were given the cyclooxygenase inhibitor, indomethacin (5 mg/kg subcutaneously), 30 min prior to topical pretreatment with 3 ml of intragastric saline, isoproterenol (3 microM), or 16,16-dimethyl prostaglandin E2 (3 microM) for 15 min. Gastric injury was induced with topical 5 mM acidified taurocholate and damage assessed by measuring net transmucosal ion fluxes, the appearance of DNA into the gastric lumen, and histology of the gastric epithelium. In a separate set of experiments, the effects of topical isoproterenol on gastric mucosal blood flow (laser Doppler flowmetry) and luminal PGE2 concentrations (125I radioimmunoassay) were examined. Pretreatment with topical isoproterenol or 16,16-dimethyl prostaglandin E2 significantly decreased bile acid-induced net luminal ion fluxes and DNA accumulation, suggesting mucosal protection. The protective effect of isoproterenol, but not 16,16-dimethyl prostaglandin E2, was negated by indomethacin (corroborated by histology). Further, isoproterenol did not significantly alter gastric mucosal blood flow, but did augment luminal PGE2 concentrations, an effect also abolished by indomethacin. Thus, isoproterenol appears to protect the gastric mucosa from the damaging effects of bile acid through a mechanism that requires the synthesis and release of cytoprotective endogenous prostaglandins.

Direct cardiac massage without major thoracotomy: feasibility and systemic blood flow.

BACKGROUND: Open-chest cardiac massage (OC-CM) provides higher blood pressure and flow than closed-chest compression and may improve the probability of successful resuscitation from cardiac arrest. Its clinical use has been limited by its requirement for a major thoracotomy. The present pilot study tested the technical feasibility of performing effective direct cardiac massage without a major thoracic incision, by using a simple, manually-powered plunger-like device, inserted through a small thoracic incision, to cyclically compress the cardiac ventricles. The method was termed minimally-invasive direct cardiac massage (MID-CM). Systemic blood flow using MID-CM was compared to that with OC-CM, by both direct systemic hemodynamic measurements, cumulative metabolic indicators of the ratio of whole body oxygen delivery and oxygen consumption, and a metabolic index of pulmonary blood flow. METHODS: In 12 large swine, baseline systemic and pulmonary hemodynamic measurements were performed. Arterial and mixed venous blood gases and metabolic indicators of systemic blood flow were measured. Ventricular fibrillation was induced and after 4 min, animals underwent either bimanual OC-CM (N = 6) or MID-CM (N = 6). At 10, 20 and 30 min, hemodynamic and metabolic measurements were repeated. RESULTS: Systemic Blood Pressure: Aortic systolic and diastolic blood pressures were reduced from baseline levels with both OC-CM and MID-CM. No difference in pressure was noted between OC-CM and MID-CM groups. Pulmonary Artery Pressure: Pulmonary artery systolic pressure was elevated from baseline during OC-CM and MID-CM. Pulmonary artery diastolic pressures remained constant throughout the resuscitation period in both groups. No differences in pulmonary systolic or diastolic pressure were noted between OC-CM and MID-CM groups. A trend towards higher pulmonary systolic pressures appeared with MID-CM. Thermodilution Blood Flow: Cardiac index fell from baseline levels with OC-CM and MID-CM. No difference in cardiac index was noted between OC-CM and MID-CM groups. Metabolic Indices: Mixed venous O2 saturation decreased from baseline levels during resuscitation in both experimental groups, with a further decrease at 30 min compared to 10- and 20-min levels. No difference was noted between OC-CM and MID-CM groups at any point. Arterial pH was reduced from baseline levels at 30 min in both groups compared to baseline but no difference was noted between groups.(ABSTRACT TRUNCATED AT 400 WORDS)

The role of calcitonin gene-related peptide and nitric oxide in gastric mucosal hyperemia and protection.

It has been suggested that capsaicin-induced hyperemia and mucosal protection occurs via calcitonin-gene-related peptide (CGRP) release from gastric afferent sensory neurons and nitric oxide (NO)-mediated vasodilation. The purpose of this study was to determine whether capsaicin and/or bile acid induced hyperemia is mediated by CGRP and/or NO. Male Sprague-Dawley rats (280-350 g) were anesthetized, and the glandular stomach (blood supply intact) was chambered between two plastic rings. Animals were divided into six groups. Normal saline (groups 1 and 4), the NO inhibitor N-nitro-L-arginine methyl ester (L-NAME; 3.75 mg/ml, groups 2 and 5), or the CGRP antagonist hCGRP8-37 (0.047 mg/ml, groups 3 and 6) was continuously infused intraarterially (ia) close to the stomach at a rate of 0.034 ml/min for 1 hr via a catheter inserted retrogradely into the splenic artery. Fifteen minutes after the onset of this infusion, the gastric mucosa was topically exposed to neutral saline solution for 15 min, followed by 160 microM capsaicin for 15 min. The mucosa was then injured by a 15-min exposure to either 5 mM acidified taurocholate (ATC, pH 1.2) in groups 1-3 or 10 mM ATC in groups 4-6. Gastric mucosal blood flow (ml/min/100 g) was continuously measured (laser doppler), and injury was assessed by measuring net transmucosal H+ flux, luminal accumulation of DNA, and histologic grading (0 = no injury to 3 = severe) by an independent observer. Intraarterial infusion of L-NAME significantly blocked the hyperemic response of topical capsaicin while having minimal effect on bile acid-induced hyperemia.(ABSTRACT TRUNCATED AT 250 WORDS)

Capsaicin-induced gastric mucosal hyperemia and protection: the role of calcitonin gene-related peptide.

BACKGROUND: Topical capsaicin augments gastric mucosal blood flow and is cytoprotective. This phenomenon is blocked by nitric oxide (NO) synthase and cyclooxygenase inhibition. Capsaicin-sensitive neurons store and release calcitonin gene-related peptide (CGRP). The purpose of this investigation was to study the effects of a CGRP antagonist on capsaicin-induced hyperemia and protection and to determine the role of NO and the cytoprotective prostaglandin PGE2 in this process. METHODS: The glandular stomachs in male Sprague-Dawley rats (280 to 350 gm) were chambered with the blood supply intact. Animals were divided into four groups. Normal saline solution (group 1) or the CGRP antagonists hCGRP8-37 (groups 2 through 4, 0.047 mg/ml) were continuously infused intraarterially via a retrograde splenic artery catheter at a rate of 0.034 ml/min after rats were given an intravenous bolus of either NSS (groups 1 and 2), L-arginine (group 3), or D-arginine (group 4) (200 mg/kg). The gastric mucosa was then topically exposed to normal saline solution (pH 7.4), followed by 160 mumol/L capsaicin and then 100 mmol/L acidified taurocholate (pH 1.2), each for 15 minutes. Gastric mucosal blood flow (ml/min/100 gm tissue) was continuously measured (laser Doppler) and mucosal injury was assessed. Luminal PGE2 production was measured during the bile acid injury period by radioimmunoassay. RESULTS: The CGRP antagonist hCGRP8-37 significantly inhibits capsaicin-induced hyperemia and its associated mucosal cytoprotection and also significantly decreases luminal mucosal PGE2 production. Pretreatment with L-arginine, but not D-arginine, reverses these effects of CGRP antagonism. CONCLUSIONS: CGRP is a mediator of capsaicin-induced hyperemia and protection. This effect may be dependent on both NO and PGE2 production.

Salt-induced hypertension in Dahl salt-sensitive rats. Hemodynamics and renal responses.

This study was performed with Dahl salt-sensitive (DS) and Dahl salt-resistant (DR) rats to detect differences in cardiovascular hemodynamics and renal responses that might be involved in initiating salt-induced hypertension in DS rats. The effects of 4 weeks of 8% NaCl diet were studied in conscious, male DR and DS rats in which vascular and urinary catheters had been previously implanted. Results were compared with those obtained from control groups of DR and DS rats on 4 weeks of 1% NaCl diet. DR rats on 8% salt diet did not develop hypertension, and cardiac output and blood volume were unchanged; glomerular filtration rate, urinary flow, sodium excretion, and plasma atrial natriuretic factor (ANF) increased. DS rats on 8% salt diet developed hypertension, and cardiac output and blood volume increased; glomerular filtration rate, urinary flow, and sodium excretion did not change, despite an increase in ANF. DS and DR rats on 1% NaCl diet were subjected to ANF infusion. After ANF infusion DR rats had a decreased blood volume and an increased glomerular filtration rate, urinary flow, and sodium excretion; DS rats showed no significant changes in blood volume, glomerular filtration rate, urinary flow, or sodium excretion. ANF caused vasodilation in all regions studied in DR rats; DS rats showed vasodilation in all regions except the kidney. After acute volume expansion, although both DR and DS rats responded by an increase in cardiac output, only DS rats developed prolonged hypertension. This finding suggests an inadequate vasodilatory mechanism in DS rats. In response to acute volume expansion, renal resistance decreased in DR rats but not in DS rats. It is concluded that the primary hemodynamic disturbance in DS rats with salt-induced hypertension is an increase in cardiac output caused by blood volume expansion in the absence of any vasodilation. Comparison of the responses of DS and DR rats to high salt diets, ANF infusion, and acute volume expansion indicates that the salt-induced hypertension in DS rats is initiated by a diminished renal response to ANF.