What Is a Urinary Drainage Bag? A Plain-Language Guide

Last verified: October 6, 2026. A urinary drainage bag is a flexible, sealed collection bag that connects to a urinary catheter and holds the urine that drains from the bladder. It is one of the most common pieces of equipment in hospitals, long-term care, and home care, and it comes in two main forms: a larger bedside bag for use when someone is in bed or seated, and a smaller leg bag worn under clothing for mobility. This guide explains what a urinary drainage bag is, its parts and types, how it differs from related devices, and what supply teams should know.

This page is general information, not clinical or safety training. Always follow your institution’s procedures and the manufacturer’s instructions for any device.

What Is a Urinary Drainage Bag?

A urinary catheter is a thin, flexible tube that carries urine out of the bladder. The catheter does not hold urine, so something has to collect it. That is the job of the drainage bag. It connects to the end of the catheter through a length of tubing, and urine flows into it by gravity. The bag has markings so that the volume can be read, and a drain port at the bottom so that it can be emptied without disconnecting it from the catheter.

Most drainage systems are designed as closed systems. The catheter, tubing, and bag are connected once and kept connected, with the bag emptied through its outlet, because opening the connection is a recognized way for germs to enter the urinary tract. The design of the bag, including its valves and ports, supports that closed approach.

Why Urinary Drainage Bags Exist

Catheters are used when a person cannot empty their bladder normally, during and after some surgeries, when urine output needs to be measured closely, or when incontinence or other conditions make other management impractical. In every case the urine needs to go somewhere that is clean, measurable, and secure. A drainage bag provides that, with a design that keeps urine flowing in one direction and keeps the outlet protected. See our guide to the Foley catheter for the most common type of catheter used with these bags.

Who Uses a Urinary Drainage Bag

Drainage bags are used by patients in hospitals and intensive care units, residents of nursing homes and long-term care facilities, and people managing a long-term catheter at home. They are used by people of all ages, including children in smaller formats. Decisions about whether a catheter is necessary, which type to use, and for how long are made by clinicians, and they are carefully considered because catheters carry a risk of infection. Our guides to catheter-associated urinary tract infection (CAUTI) and urinary catheter types and selection give broader context.

Main Parts of a Urinary Drainage Bag

• Connector and tubing: the length of tubing that joins the catheter to the bag, usually with a standard tapered connector.
• Anti-reflux valve: a one-way valve, often in a drip chamber, that helps stop urine from flowing back toward the bladder.
• Sampling port: a needle-free port on the tubing from which a sample can be taken without opening the system.
• Drainage outlet or tap: the port at the bottom of the bag used for emptying, which closes with a clamp, tap, or other closure.
• Volume graduations: printed marks that show how much urine the bag contains.
• Hanger or strap: a way of hanging the bag from a bed frame or chair, or of securing a leg bag with straps.
• Backing material: some bags have a soft, non-woven backing for comfort against the skin.

Types of Urinary Drainage Bags

Bedside (Large-Capacity) Bags

These larger bags hang from a bed frame, chair, or stand and are used when a person is in bed, resting, or at night. They hold more urine than a leg bag, so they need emptying less often and are the standard choice in hospital wards and for overnight use. They should be kept below the level of the bladder so that urine drains downward, and they should not rest on the floor.

Leg Bags

Leg bags are small and strapped to the thigh or calf under clothing, which makes them suitable for people who are up and moving. They have a shorter tube and a smaller capacity, so they need emptying more often. Many people use a leg bag during the day and switch to a bedside bag at night, following their care team’s guidance.

Urometer or Hourly-Output Bags

In intensive care and other settings where urine volume is measured closely, a bag with a small graduated chamber at the top, called a urometer, allows hourly measurements without emptying the main bag each time. The chamber empties into the larger bag.

Drainable vs. Non-Drainable and Sterile Packaging

Most bags have a drainage outlet and are intended for the duration of use before replacement. Bags are supplied sterile and are intended for single-patient use, and many catheter kits and trays include a pre-connected bag. Pediatric and other smaller-volume bags are also manufactured.

How a Urinary Drainage Bag Differs from Related Devices

• Drainage bag vs. ostomy bag. A drainage bag connects to a catheter or tube. An ostomy bag sticks directly onto the skin around a surgically created opening called a stoma, and collects its output without a catheter.
• Drainage bag vs. Foley catheter. The catheter is the tube that goes into the bladder, and the drainage bag collects what comes out. They are used together but are separate items.
• Drainage bag vs. bedpan. A bedpan is a container for people who need to pass urine or stool while in bed. It is used for ordinary voiding and is emptied after each use, rather than receiving continuous drainage through a tube.
• Drainage bag vs. suction canister. A suction canister collects fluid pulled by a suction source. A urinary drainage bag relies on gravity.

Everyday Handling in General Terms

Because a catheter drainage system sits at the border between the inside of the body and the outside world, general handling principles are widely taught. At a high level, they include keeping the system closed, keeping the bag below bladder level and off the floor, avoiding kinks or loops in the tubing that can block flow, emptying the bag through its outlet rather than disconnecting it, and keeping the drainage outlet from touching the collecting container or any surface. Staff and caregivers are trained in these practices and in hand hygiene, and facilities audit them as part of infection-prevention programs. The details differ by setting and product, and the manufacturer’s instructions and local policy are the authority.

For anyone responsible for equipment rather than patients, these principles explain why product design features such as secure outlets, hangers that keep the bag off the floor, and clear volume markings are not trivial extras. They support the practices that infection-prevention programs are trying to achieve.

Practical Relevance for Research Administration and Procurement

Drainage bags are simple, high-volume consumables, and a few practical points affect how they are specified and tracked.

First, specify the type. Bedside, leg, and urometer bags are different products, and each comes in different capacities, tubing lengths, and outlet styles. Ordering by “urine bag” alone often leads to the wrong product.

Second, compatibility matters. The connector must fit the catheter in use, and some catalogs offer bags pre-attached to catheters in kits. Facilities usually standardize on a limited range so staff can find compatible items quickly. For more on how these items are grouped for stocking, see our guide to drainage catheters and institutional stocking.

Third, infection prevention affects purchasing. Because catheter-associated infections are a recognized quality and safety concern, many facilities track catheter use and monitor bundles of practices. Product features such as anti-reflux valves, needle-free sampling ports, and secure outlets are often evaluated in purchasing decisions. A CAUTI prevention bundle is one example of the kind of program in which these products are used.

Fourth, bags are single-patient items that are changed or replaced on schedules set by the manufacturer and facility policy, so consumption follows census and catheter-days. In research, catheter and bag use may be recorded as part of safety or outcome data, and consistent product records help.

Frequently Asked Questions

What is a urinary drainage bag?

It is a sealed collection bag that connects to a urinary catheter and holds the urine that drains from the bladder.

What is the difference between a leg bag and a bedside bag?

A leg bag is small and worn under clothing so that a person can move around, but it needs emptying more often. A bedside bag is larger, hangs from a bed or chair, and is used when resting or overnight.

Why should the bag be kept below the bladder?

The system relies on gravity to move urine into the bag. Keeping the bag lower than the bladder supports drainage and helps prevent urine from flowing back, as part of general catheter care guidance. Specific instructions come from the care team and the manufacturer.

Why are drainage systems kept closed?

Disconnecting the catheter from the tubing can introduce germs into the urinary tract. Closed systems, with bags emptied through an outlet, are designed to reduce that risk.

How often is a drainage bag emptied?

It depends on how much urine the person produces and the size of the bag. Bags are emptied before they become full, following facility procedures or the care team’s instructions.

Can a drainage bag be reused?

Bags are generally for single-patient use and are replaced following the manufacturer’s instructions and facility policy. They are not intended to be shared or reprocessed between people.

Who decides if someone needs a catheter and drainage bag?

The decision is made by a clinician based on the person’s condition. Catheters are generally used only when needed and for as short a time as appropriate, and this guide cannot advise on individual cases.