Approach to ascites: Clinical sciences

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Introduction0:00–1:03

Ascites refers to an abnormal collection of fluid in the peritoneal cavity, which can be a sign of various underlying conditions.
In some cases, ascites can arise in the absence of portal hypertension, which is typically seen in conditions such as peritoneal carcinomatosis; pancreatic ascites, protein-losing enteropathy, and nephrotic syndrome.More commonly, ascites is associated with portal hypertension, which can occur due to prehepatic, hepatic, and posthepatic causes.
The most common prehepatic cause is portal vein thrombosis; while common hepatic causes include cirrhosis, infiltrative liver disease, and acute liver failure.
Finally, important posthepatic causes include right-sided heart failure, constrictive pericarditis, and pulmonary hypertension.Now, when approaching a patient with new ascites, you should first obtain focused history and physical examination, as well as labs, including CBC, CMP, and coagulation profile.

Focused H&P, Labs, Abdominal US, Diagnostic paracentesis1:03–2:28

History typically includes progressive abdominal distension; while physical exam reveals bulging flanks, a palpable fluid wave, and shifting dullness to percussion.Additionally, order an abdominal ultrasound, which can help you detect free fluid in the peritoneal cavity, which is commonly seen as an anechoic space.Next, obtain a diagnostic paracentesis to remove a small amount of ascitic fluid for analysis.
Initial tests on the ascitic fluid include albumin, total protein, and cell count with differential. With these values, calculate the serum ascites albumin gradient, or SAAG for short, by subtracting the ascites albumin from the serum albumin.
The SAAG results will help you determine if portal hypertension is present or absent. Moreover, SAAG less than 1.1 means there’s no portal hypertension, so your next step is to assess the ascitic fluid WBC count and differential.Elevated WBCs in ascitic fluid with predominant lymphocytes should make you think of peritoneal disease, so test ascitic fluid for TB cultures and order cytology.

Peritoneal disease2:28–3:02

Positive cultures confirm the diagnosis of peritoneal tuberculosis; while positive cytology for malignant cells confirms the diagnosis of peritoneal carcinomatosis.
Keep in mind that peritoneal carcinomatosis can be caused by a primary cancer of the peritoneum, but more often it happens when cancer metastasizes to the peritoneum.Ok, let’s say the ascitic fluid has elevated WBCs, but the differential reveals a neutrophilic predominance.
In this case, you should consider pancreatic ascites or secondary bacterial peritonitis. Individuals with pancreatic ascites may have a history of chronic pancreatitis, or they may have suffered recent abdominal trauma.To differentiate the two, measure ascitic amylase level and order ascitic fluid cultures.

Pancreatic Ascites/Secondary bacterial peritonitis3:02–3:57

High amylase confirms the diagnosis of pancreatic ascites. On the other hand, positive ascitic fluid cultures for more than one pathogen, or in other words, positive polymicrobial cultures, confirm the diagnosis of secondary bacterial peritonitis.
Secondary bacterial peritonitis occurs when bacteria from an underlying intraabdominal infection spread to the peritoneal cavity.Finally, let’s take a look at patients that present with normal WBC count with lymphocyte predominance.
If your patient presents with ascites and a history of diarrhea, steatorrhea, or abdominal bloating, in combination with pitting edema, consider protein-losing enteropathy.In this case, order a 24-hour stool alpha-1 antitrypsin test to evaluate for excessive protein loss in the stool.

Protein-losing enteropathy3:57–4:34

Elevated alpha-1 antitrypsin confirms the diagnosis of protein-losing enteropathy.But, what if your patient presents with a history of frothy urine and facial edema?
In this case, consider nephrotic syndrome. To confirm the diagnosis, you should order a urinalysis and 24-hour urine protein.

Nephrotic syndrome4:34–5:04

Urinalysis in a patient with nephrotic syndrome will show greater than 3.5 g of protein per 24 hours, as well as lipiduria.Now, let’s go back to the SAAG and take a look at individuals with SAAG equal to or greater than 1.1, which is suggestive of portal hypertension.
In these individuals, your next step is to assess the ascitic fluid total protein and determine whether or not the cause of portal hypertension is a liver problem.If the ascitic fluid total protein is equal to or greater than 2.5 g/dL, there’s a low likelihood of liver conditions, so consider posthepatic causes.These individuals typically report dyspnea on exertion, while their physical exam usually reveals jugular venous distention, bilateral lower extremity edema, and hepatomegaly.

Posthepatic causes5:04–6:41

If your patient presents with these findings, order a transthoracic echocardiogram, or TTE for short. TTE can help you detect elevated pressure in the right side of the heart, which is associated with increased central venous pressure and conditions such as right-sided heart failure, constrictive pericarditis, and pulmonary hypertension.Now, here’s a high-yield fact!
An important auscultatory finding in individuals with constrictive pericarditis is pericardial knock, which refers to a high-pitched sound that occurs in early diastole as a result of sudden cessation of ventricular filling.Now, let’s go back to the ascitic fluid total protein levels and take a look at individuals that have less than 2.5 g/dL.
If this is the case, assess ascitic fluid polymorphonuclear count, or PMN count for short.PMN predominance is suggestive of spontaneous bacterial peritonitis, which is an infection of ascitic fluid, and is a common complication in patients with cirrhosis and portal hypertension.

Spontaneous bacterial peritonitis6:41–7:46

In contrast to secondary bacterial peritonitis, in spontaneous bacterial peritonitis, there’s no other clear source of infection.
Your next step is to order ascitic fluid cultures. Often these individuals will present with signs and symptoms suggestive of infection, such as fever and malaise.
Ascitic fluid cultures positive for just one pathogen, or in other words, monomicrobial cultures, confirm the diagnosis of spontaneous bacterial peritonitis.On the other hand, some individuals can have ascitic fluid with no PMN predominance.
In this case, think of either pre hepatic or hepatic causes of portal hypertension. First, let’s start with prehepatic causes like portal vein thrombosis.
To confirm the diagnosis, order doppler US, which will reveal either reduced or absent portal venous flow.Finally, let’s take a look at the most common hepatic causes of portal hypertension, such as acute liver failure, infiltrative liver disease, and cirrhosis.

Portal vein thrombosis7:46–8:12

Let’s start with acute liver failure.These patients usually present with new ascites and a history of right upper quadrant pain.
Additionally, always ask about acetaminophen use, which is the medication most commonly associated with acute liver failure.

Acute Liver Failure8:12–9:02

Physical exam might reveal altered mental status, jaundice, and hepatomegaly. Finally, when checking lab results, be sure to check viral hepatitis serologies.
Additionally, keep an eye on very high aminotransferases and a prolonged prothrombin time; and if INR is greater than 1.5, you can make a clinical diagnosis of acute liver failure.Now, switching gears and moving on to infiltrative liver disease, which includes hepatocellular carcinoma and liver metastases, as well as sarcoidosis, amyloidosis, hemochromatosis, Wilson disease, and alpha-1 antitrypsin deficiency.
These individuals often are asymptomatic until their disease evolves to cirrhosis. Those who do have symptoms may complain of abdominal pain or fullness in the right upper quadrant, as well as nausea, anorexia, and unintentional weight loss.The next step is to do an abdominal ultrasound to evaluate the liver parenchyma; but if the abdominal ultrasound findings are not clear, order a contrast-enhanced CT or MRI.

Infiltrative liver disease9:02–9:55

Lastly, you may need to get a biopsy to confirm the diagnosis.Finally, let’s take a look at cirrhosis. These individuals generally present with new ascites and a history of alcoholic or viral hepatitis; while physical exam findings typically include jaundice, spider angiomas, and palmar erythema.
Labs usually show elevated aminotransferases, bilirubin, prothrombin time, and sometimes thrombocytopenia.On abdominal ultrasound, the liver appears small and nodular.
All of these findings are highly suggestive of cirrhosis, but if you are still not sure, you can order an ultrasound elastography or liver biopsy to confirm the diagnosis.

Cirrhosis9:55–11:36

Ultrasound elastography estimates liver elasticity and subsequently determines the degree of liver fibrosis. There will be increased liver stiffness in cirrhosis.
Alternatively, you can perform a liver biopsy, which is the gold standard for diagnosis, to detect regenerative nodules surrounded by fibrotic tissue.Now, here’s a high-yield fact to keep in mind!
If your patient comes from tropical parts of the world, such as Africa, South America, or Southeast Asia, consider schistosomiasis, which is an infectious condition caused by a parasitic flatworm.
People with chronic schistosomiasis can develop fibrosis of the liver around the portal vein, which can eventually result in portal hypertension.
Microscopic examination of the stool showing schistosomal eggs confirms the diagnosis.Alright, as a quick recap… Ascites can be a sign of various underlying conditions and diagnostic paracentesis can help you identify the cause.
First, calculate the SAAG to determine if portal hypertension is present or absent. SAAG less than 1.1 means there’s no portal hypertension, so your next step is to assess the ascitic fluid WBC count and differential, which will help you identify conditions such as peritoneal tuberculosis and carcinomatosis; pancreatic ascites; secondary bacterial peritonitis; protein-losing enteropathy; and nephrotic syndrome.On the other hand, SAAG equal to or greater than 1.1 is suggestive of portal hypertension, so your next step is to assess the ascitic fluid total protein and determine whether or not the cause of portal hypertension is a liver problem.

Review11:36–13:13

If the ascitic fluid total protein is equal to or greater than 2.5g/dL, there’s a low likelihood of liver conditions, so consider posthepatic causes, such as right-sided heart failure, constrictive pericarditis, and pulmonary hypertension.
But, if the ascitic fluid total protein is less than 2.5 g/dL, assess PMN count, since PMN predominance is suggestive of spontaneous bacterial peritonitis.On the flip side, if the PMN is not predominant, consider prehepatic causes, such as portal vein thrombosis, or hepatic causes, like acute liver failure, infiltrative liver disease, and cirrhosis.
protein is equal to or greater than 2.5 g per deciliter there's a low likelihood of liver conditions So consider posthepatic causes such as right sided heart failure constrictive pericarditis and pulmonary hypertension But if the acidic fluid total protein is less than 2.5 G assess PMN count since PMN predominance is suggestive of spontaneous bacterial peritonitis On the flip side If the PMN is not predominant consider prehepatic causes such as portal vein thrombosis or hepatic causes like acute