If there’s one sentence guaranteed to prompt panic, it’s when your 3-year-old grandson says, “I gotta go potty.”

Especially when he’s days out of diapers and his grandparents aren’t quite sure how frequent he has to make those bathroom visits.

Under normal conditions potty training for the tot is not a problem around the Fisher household. When we hear the potty cry, we hustle little Zachary to the rest room and offer tons of praise when he proves to us that he’s ready to ditch the diaper.

Like every good grandparent, we learned the moves to the Potty Dance and sing along to encourage Zachary to pull down his Pull-Ups for good.

But panic set in Wednesday when grandpa Eric and grandma Janet heard those new-learned words coming from Zach who was crossing his legs in the back seat of our car.

We were rolling into Chicago and grandpa Eric had just turned off the Stevenson Expressway onto the Dan Ryan. As expected, traffic on the six lanes were backed up bumper-to-bumper.

My bride of 26 years gave me a wide-eyed look. “Eric can you just take the next exit or something?”

My response wasn’t what she wanted to hear. “Are you serious? You think I can just honk the horn and everybody’s going to just let me through?”

That’s when I focused on the “or something” part of the Queen’s request.

I had an immediate flashback to when I was a youngster growing up in Iowa. Our family of 10 would pile into a station wagon for summer vacations to Minnesota. Our 10-hour trip was rarely taken without an empty quart-size Mason jar.

The Mason was there for emergency measures and the first lad to announce he needed to go to the bathroom was usually handed the jar. I don’t recall any of us being humiliated enough to use it, but the end result was typically you learned to hold it for another 100 miles or so.

“Eric!” Janet snapped, “What are you going to do?”

I grabbed a full water bottle and after chugging it, handed it to Grandma Janet who was in the back seat with Zachary.

“Here, have him use this,” I said.

Shaking his head, little Zach said, “Grandpa I have to go potty and I can’t use that.”

“OK you’ll just have to hold it a little bit longer,” I told Zachary.

Once we got past the I-290, traffic cleared up enough for us to exit two miles ahead on Washington Blvd. Our destination was Chicago City Hall  a mile to the east. But as luck would have it, there were detours through the downtown and we were going to be cutting it close for a noon appointment.

“We’re getting close,” I informed Zachary as a taxi cut me off, honking its horn.

The closer we got into the heart of the city the more chaotic it was with pedestrians hustling through intersections and buses running their routes. Two closed streets and a one-way route forced us north away from city hall.

“How much longer Grandpa?” I heard from the back seat. “I can’t wait.”

I zipped through the Clark Street intersection and found LaSalle where I turned right.

“There it is Zachary, we’re here,” I exclaimed.

I pulled up curbside to allow Janet and Zach the shortest  run to the front door. That’s when I realized my emergency maneuvers with chugging the water bottle were beginning to backfire. Suddenly it was grandpa who wanted to yell, “I have to go potty.”

I combed through two blocks looking for a parking place. No luck. I circled back hoping not to get lost and find a spot. Time was running out and as inviting as the empty water bottle was, it was not an option. I found a parking garage one block away from city hall and after finally finding an empty spot 12 stories up, I parked and exited our vehicle.

At this point I must have looked like the late great Walter Payton as I hit the ground floor running. I dodged and wove through the lunchtime crowd during a sidewalk sprint to city hall.

Great, no rest rooms on the ground floor. Janet buzzed my cell phone to inform me that she had made the appointment and took care of business. She and Zachary were waiting on the fifth floor.

A speedy elevator got me there and when the doors open there sat a smiling Zachary.

“Grandpa, here we are,” he said. But my priority was finding the rest room and I asked Janet where it was.

“I know where it is,” the 3-year-old proudly said. “I’ll show you Grandpa cause I already went there.”

I said, “Please show me,” to Zachary, “I have to go real bad.”

He grabbed my hand and led me down the hall. Zachary looked up with his bright blue eyes and said, “Grandpa, you could have used the water bottle in the car.”

Laughing, I replied, “No Zachary, people don’t really do that.”