Diagnosing the crop disorder
A hen is behaving lethargically, not eating much, if at all, but she has a full crop. This is the first sign something's not right. The full crop points to this hen having crop issues and not being sick for some other reason such as a bacterial infection, which would result in loss of appetite and empty crop.

Before you treat for a crop issue, though, you need to verify that your hen or roo actually has a crop issue and whether it's sour crop or impacted crop or both. So you need to monitor the crop overnight, checking the condition before bedtime, and first thing in the morning before your patient eats anything.

Sour crop
A crop that is still full in the morning has issues. So, is the issue sour crop? If the crop feels squishy and full of liquid, it's likely sour crop. If there's an odor coming from the head of the chicken that smell similar to sauerkraut, then you are probably dealing with sour crop. The cause is a yeast called Candida albicans.

Impacted crop
If the crop is extremely full and hard, or perhaps lumpy, and maybe feels like it's full of fibrous material, you are probably looking at impacted crop. If the chicken has been drinking lots of water, yet not eating anything, this is further indication of impacted crop.

Impacted crop/sour crop
If the crop is full and hard and lumpy and the chicken has been drinking lots of water and it smells like sauerkraut, you likely have an impacted crop that has developed a yeast infection. You will be treating the impacted crop first, followed by treatment for the yeast infection.

Treatment for impacted crop
I use coconut oil for the ease in administering it. When chilled, it is solid and easy to break into small chunks and slip into the beak of the patient without creating a huge mess or getting oil into the airway. You want to measure two teaspoons for an adult chicken and one teaspoon for a baby chick.

After getting the oil into the patient, you want to massage the crop gently in a circular and slightly upward motion. This will direct the contents toward the crop "drain". Massage for five to ten minutes. If the crop refuses to empty, repeat the oil and massage again in 30 minutes. If the crop still refuses to empty, then give a stool softener docusate sodium. Do not use a laxative as it would cause cramping and is too harsh for a chicken. Wait 30 minutes and massage the crop. The crop should empty. Add more oil if it doesn't and massage again. This should do it.

Treatment for sour crop
I advise against trying to make your chicken vomit because it may cause them to aspirate the sour liquid. Besides, it's very unpleasant for your hen, and she may hate you if you do it. (Curiously, most sour crop victims are hens.)

Nystatin is the best treatment for yeast infections, but it requires a prescription. Or you can try to locate medistatin which is for birds and doesn't require a prescription.

The easiest (and cheapest) to obtain yeast treatment, though, is miconazole, found on the women's hygiene shelf in the pharmacy. You can use either the suppositories or the vaginal cream. Measure a quarter inch of suppository or about half an inch of cream and give orally twice a day for seven days. Do not stop treatment before the full seven days are completed or the yeast may return.

You may see different strengths of miconazole, 2% or 4%, and wonder which to get. Either strength is fine. I prefer the 2% cream myself for economic reasons. The treatment with either strength is the same, twice and day for a full seven days.

Following treatment for sour crop, offer plenty of plain fresh water and boiled egg to get the crop operating again. I like to also give a probiotic or Greek yogurt to restore good microbes in crop and intestines.

Pendulous crop
If you have treated for these crop issues and the crop still refuses to empty by morning, the hen may have a condition called pendulous crop. This is caused by poor muscle tone that causes the crop to sag and the contents are below the crop "drain" so the crop doesn't fully empty. The solution is a crop bra.

You can buy these or easily create one yourself by gluing or sewing a four inch square piece of sturdy cloth to two twelve-inch long strips of elastic bandage such as Vet wrap.

Addendum: Since I originally wrote this article, I've been involved in coaching two extremely serious cases where the miconazole treatment or impacted crop treatment failed to clear the crop. There are a couple of reasons why it can fail. One is that there is an underlying health issue far more serious that is shutting down the chicken's bodily functions. The other reason is that the crop obstruction goes all the way down the digestive tract and is impacting the gizzard, too.

When this is the case, it's usually fatal. However, in each of these two cases, the chicken care giver was agreeable to performing crop surgery. (Perhaps a subject for a future article.) In both cases the surgery was successful in clearing the crop of the obstruction. However, the chicken in each case was still not showing signs of recovery, so the next step was to do a molasses flush. This was successful in both cases in flushing out the impacted gizzard. Without these drastic measures, both chickens would have almost certainly died.

When normal crop treatments fail, crop surgery and flushing the gizzard are last resort options that may be tried in lieu of euthanizing the chicken or letting it die.

Here's is a thread I made with instructions on making a properly fitted crop bra, step by step with photos and measurements. https://www.backyardchickens.com/threads/making-a-crop-bra-for-a-hen-with-pendulous-crop.1464848/

Update: This is in reference to the elderly hen I previously made the crop bra for. Lilith is now twelve years old, and she's old and tired. (Like me.) For the past three weeks, she's been tired and listless. I gave up on the crop bra because it didn't seem to make a difference. Her crop has been full and lumpy but never sour or impacted. What it is, I've discovered, is slow and tired like she and I. So, I've been periodically giving her brief crop massages throughout the day, perhaps three or four. It takes maybe 45 seconds each.

After each massage, Lilith has become energized. She immediately feels like eating. Due to this, her food intake has increased and her energy level has also increased. She has gone from barely alive to a hen who is now coming off her lounging cushion and stepping out of the run to join the other chickens in competing for treat toss.

To sum it up, if you have a chicken with a chronic crop issue, give this a try. Pick up your chicken and do a gentle massage of the crop. It takes less than one minute. This, I believe, will rejuvenate the crop and improve function. While it may not cure a chronic crop disorder, it will improve it, and your chicken will feel much better than they did before. Best of all, it's simple, easy, non-toxic, and doesn't cost any money.