The goal of this observational study is to learn how liver cirrhosis affects the diaphragm, the main muscle used for breathing, in adults. The study will measure diaphragmatic thickness, thickening fraction, and excursion using bedside ultrasound and compare these values between patients with cirrhosis and healthy volunteers. The main questions it aims to answer are:

Do patients with cirrhosis show reduced diaphragmatic function compared to healthy adults?

Does removal of ascitic fluid by paracentesis improve diaphragmatic mechanics?

Can ultrasound measurements of the diaphragm serve as a reliable non-invasive marker of sarcopenia when compared to CT scans?

Participants will:

Undergo diaphragmatic ultrasound during quiet and deep breathing

Provide clinical and laboratory data related to liver disease severity

In some cases, have ultrasound repeated before and after paracentesis

For patients with hepatocellular carcinoma, CT scans will be analyzed to measure muscle mass

This study is a prospective observational cohort designed to evaluate diaphragmatic structure and function in adults with liver cirrhosis. Using bedside ultrasound, the study will measure diaphragmatic thickness, thickening fraction, and excursion, and compare these values across different stages of liver disease severity and complications such as ascites, hepatic hydrothorax, and hepatocellular carcinoma. A subgroup of patients undergoing large-volume paracentesis will have ultrasound assessments before and after fluid removal to determine the acute impact of ascites drainage on diaphragmatic mechanics. In patients with hepatocellular carcinoma, existing CT scans will be analyzed to calculate skeletal muscle index, allowing correlation between ultrasound parameters and sarcopenia. Healthy volunteers will serve as a reference group for establishing normative values. Clinical and laboratory data, respiratory outcomes, and hospitalization details will also be collected to explore associations between diaphragmatic dysfunction and patient prognosis. The study aims to validate diaphragmatic ultrasound as a simple, non-invasive tool for respiratory monitoring and sarcopenia assessment in cirrhosis, particularly in resource-limited settings.

Inclusion Criteria:

1. Age ≥18 years.
2. Confirmed diagnosis of liver cirrhosis based on clinical, biochemical, histological, or imaging criteria.
3. Ability to provide written informed consent in Arabic or English.
4. For Subgroup A: clinical indication for large-volume paracentesis with an ascitic volume of ≥5 liters.
5. For Subgroup B: confirmed hepatic hydrothorax or confirmed absence of pleural effusion on ultrasound or chest X-ray.
6. For Subgroup C: radiologically confirmed HCC by triphasic CT or MRI according to EASL/AASLD diagnostic criteria, with available CT imaging for L3 SMI analysis.

Exclusion Criteria:

1. Significant pre-existing primary pulmonary disease (e.g., moderate-to-severe COPD defined as FEV1/FVC <70% with FEV1 <60% predicted, interstitial lung disease, pulmonary fibrosis) that independently affects diaphragmatic mechanics.
2. Recent thoracic surgery, thoracocentesis within the preceding 72 hours, or thoracic trauma.
3. Neuromuscular disease (e.g., myasthenia gravis, amyotrophic lateral sclerosis, Guillain-Barré syndrome) independently affecting diaphragmatic function.
4. Active mechanical ventilation at time of enrollment.
5. Pregnancy.
6. Inability to achieve adequate ultrasound acoustic windows (e.g., due to extreme obesity or surgical dressings).
7. Contraindications to paracentesis in Subgroup A (e.g., disseminated intravascular coagulation, bowel obstruction).
8. Prior or planned liver transplantation within the study period, which would confound longitudinal follow-up.
9. Refusal or inability to provide informed consent.

Adults (≥18 years of age) with confirmed diagnosis of liver cirrhosis attending the hepatology outpatient clinic or admitted to the hepatology inpatient unit of the study institution.

Study Subgroups The total study sample will consist of 120 participants, including 95 patients with liver cirrhosis and 25 healthy controls. The cirrhotic cohort will include patients across different Child-Pugh classes and MELD scores and will encompass clinically relevant subgroups such as patients with ascites undergoing paracentesis, hepatic hydrothorax, and hepatocellular carcinoma (HCC).

• Subgroup A: Ascites/Paracentesis (n=30): Patients with tense or refractory ascites for whom large-volume paracentesis is clinically indicated. This subgroup will contribute both cross-sectional and longitudinal (pre/post paracentesis) data.
• Subgroup B: Hepatic Hydrothorax (n=40): Twenty patients with confirmed hepatic hydrothorax (HH; defined as pleural effusion >500 mL in the absence of primary cardiopulm